NOVELTY - A water turbine anti-cavitation improving technique is performed by (1) carrying out sand blasting on whole rotating wheel, blade, and tail water lining of drain pipe or discharge pipe until a standard Sa2.5 grade is reached; (2) adopting titanium-containing stainless steel embedding method or pinning and polyurethane elastomer coating method for repairing the turbine rotating wheel, blade and tail water pipe erosion pit; and (3) coating with plastic steel 8103 wearable anti-cavitation coating and plastic steel 8102 ultra smooth coating.    USE - Anti-cavitation improving technique for water turbine (claimed).    ADVANTAGE - The method is energy-saving; can effectively improve the output, cavitation resistance and abrasion resistance of water turbine; and can prolong the overhaul period of water turbine.    DETAILED DESCRIPTION - A water turbine anti-cavitation improving technique is performed by (1) carrying out sand blasting on whole rotating wheel, blade and tail water lining of drain pipe or discharge pipe until a standard Sa2.5 grade is reached; (2) adopting titanium-containing stainless steel embedding method (I) or pinning and polyurethane elastomer coating method (II) for repairing turbine rotating wheel, blade and tail water pipe erosion pit; and (3) coating with plastic steel 8103 wearable anti-cavitation coating (A) and plastic steel 8102 ultra smooth coating (B). The titanium stainless steel embedding method (I) in step (2) is performed by cleaning the sand blasted erosion pit; adhering a piece of paper on the erosion pit, using a pen to draw an outline of the erosion pit on the paper; manufacturing 321 titanium stainless steel spare parts according to the paper drawn pattern, making the spare parts size less than the pattern to enable convenient installation; adopting tapping wire method or assay fastening to form screw holes with 30-mm screw, drilling the corresponding holes on the titanium-containing stainless steel spare parts; filling the whole sand blasted erosion pit with plastic steel 8201 epoxy molding repairing material (C); installing the titanium stainless steel spare parts with screw, and cutting off excess part of the screw and end head to obtain titanium stainless steel edge-plastic steel 8201 epoxy molding repairing material. The pinning and polyurethane elastomer coating method (II) in step (2) is performed by cleaning the sand blasted erosion pit; butt-welding nails with specific shape on the cavitation area at a nail welding density of 600-1000 nails/m2; spraying a solvent-based epoxy-polyamide anti-corrosion paint on the sand blasted or abrasive region; coating with nano-polyurethane elastomer repairing material (D); drying the polyurethane elastomer material and trimming excess material to finish the repairing process. The nano-polyurethane elastomer repairing material (D) comprises (wt.%) Bayer 1062 flexible polyester polyol methylene diphenyl diisocyanate (MDI) prepolymer (50-60); Bayer 1200 polycarbonate polyol (15-20); 1,4-butanediol (5-8); triethylenediamine (2-4); gas phase silicon dioxide (1-2); and red iron oxide (15-25). The plastic steel 8201 epoxy molding repairing material (C) comprises (wt.%) Shell 828 liquid epoxy resin (18-23); phenolic aldehyde amine curing agent 2003D (8-10); ferro-silicon alloy powder with 15 % silicon content (50-55); 100-mesh silicon carbide (8-13); talc powder (6-10); gas phase silicon dioxide (1-2); and tris(dimethylaminomethyl)phenol (0.5-1). The plastic steel 8103 wearable anti-cavitation coating (A) comprises (wt.%) Shell 828 liquid epoxy resin (18-22); epoxy-terminated butadiene-nitrile rubber (5-7); phenolic aldehyde amine curing agent 2003D (9-12); ferro-silicon alloy powder with 15 % silicon content (45-52); 100-mesh silicon carbide (8-13); and talc powder (3-5). The plastic steel 8102 ultra smooth coating (B) comprises (wt.%) Shell 828 epoxy resin (35-40); epoxy adduct isophorone diamine (24-30); nano-polytetrafluoroethylene (3-6); nitrogen-doped nano titanium dioxide (3-5); red iron oxide (9-13); glass flake (12-15); and talc powder (8-12). The coating region for the anti-cavitation coating (A) and ultra smooth coating (B) in step (3) comprises the rotating wheel, blade and inner pipe but does not include the polyurethane elastomer repairing region. The total thickness of the anti-cavitation coating (A) and ultra smooth coating (B) is 400-600 mu m.