NOVELTY - A multilayer biaxially oriented white polyester film comprises three polyester layers, a core layer and same or different two outer layers, and titanium dioxide particles, one layer comprising a polyethylene terephthalate with a number average molecular weight of 18500-40000, 19000-35000 and 20000-30000, intrinsic viscosity IV (dL/g) in an increasing order of greater than or equal to 0.70, greater than or equal to 0.75, greater than or equal to 0.78 and 0.78- 1.20, and carboxyl group content (q/T) in an increasing order of less than or equal to 30, less than or equal to 25, less than or equal to 21, less than or equal to 15 and 5-15.    USE - Multilayer biaxially oriented white polyester film for use in laminate and back sheet of solar or photovoltaic cell (all claimed) as protective film.    ADVANTAGE - The film has better adhesion, absence of chalking, better opacity whiteness, better reflectance, better hydrolysis resistance and better light stability, better thermal stability, better dimensional stability, better chemical resistance and relatively high surface energy, and is inexpensive, and provides the cell with better durability.    DETAILED DESCRIPTION - A multilayer biaxially oriented white polyester film comprises three polyester layers, a core layer and same or different two outer layers, and titanium dioxide particles, one layer comprising a polyethylene terephthalate with a number average molecular weight of 18500-40000, 19000-35000 and 20000-30000, intrinsic viscosity IV (dL/g) in an increasing order of greater than or equal to 0.70, greater than or equal to 0.75, greater than or equal to 0.78 and 0.78- 1.20, and carboxyl group content (q/T) in an increasing order of less than or equal to 30, less than or equal to 25, less than or equal to 21, less than or equal to 15 and 5-15, where the core layer comprises titanium dioxide particles (w/w)% in an increasing order of 0.1-40, 0.5-30, 1-20 and 2-10, and intrinsic viscosity IV (dl/g) of the film in an increasing order of 0.5-0.85, 0.55-0. 8, 0.6-0.75, and 0.65-0.75, the small endothermic peak temperature, Tmeta measured on the film is 180-230 degrees C, preferably 180-220 degrees C, one of the outer layers is added with one light stabilizer with concentration ranges ((w/w)%) in an increasing order of 0.1-35, 0.2-25, 0.3-20, 0.4-10 and 0.5-5. INDEPENDENT CLAIMS are also included for the following:    (1) a method for manufacturing a multilayer biaxially oriented white polyester film    (2) a laminate    (3) a solar or photovoltaic cell having a back sheet.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a photovoltaic cell.    Total light transmission material (1)    Photovoltaic battery (2)    Filled resin (3)    Photovoltaic battery backside protection laminate (4)    Lead wire (5)