NOVELTY - Waste molasses or waste glucose mother liquid is used to produce welan gum by filling seed liquid into a fermenting medium to carry out fermentation with seed liquid and fermenting medium ratio of 15-30%. The fermenting medium includes (pts.wt.) waste molasses or waste glucose mother liquid (3.55-4.2)%, enzymolysis cotton seed protein (0.15-0.2), soybean protein peptide (0.1-0.2), soybean powder (0.1-0.2), potassium hydrogen phosphate (0.1-0.2), calcium carbonate (0.15-0.25), iron sulfate (10-15 ppm), and polyether anti-foam agent (0.05-0.1).    USE - Method of using waste molasses or waste glucose mother liquid to produce welan gum.    ADVANTAGE - The method resolves severe pollution problem.    DETAILED DESCRIPTION - Use of waste molasses or waste glucose mother liquid to produce welan gum involves: (A) preparing seed liquid with incline strain, e.g. Sphingomonas sp; (B) filling the seed liquid into a fermenting medium to carry out fermentation with seed liquid and fermenting medium ratio of 15-30%, where the fermenting medium includes (pts.wt.) waste molasses or waste glucose mother liquid (3.55-4.2)%, enzymolysis cotton seed protein (0.15-0.2), soybean protein peptide (0.1-0.2), soybean powder (0.1-0.2), potassium hydrogen phosphate (0.1-0.2), calcium carbonate (0.15-0.25), iron sulfate (10-15 ppm), and polyether anti-foam agent (0.05-0.1); (C) fermenting for 10 or 20-30 hours at 28-32 degrees C, at 0.03-0.05 MPa, pH of 7.1-7.2, ventilating amount of 0.2-0.3 or 0.4-0.5 vvm; (D) adding soybean protein peptide, and controlling the ammonia nitrogen to 0.00045-0.0006% at 28-32 degrees C and at 0.03-0.05 MPa, pH of 7-7.5, and ventilating amount of 0.5-0.6 vvm; (E) adding basic salt or weak base whose concentration is 1-3% for 60-65 hours to make pH of 7.2-7.5, and ventilating amount of 0.5-0.6 vvm; (F) obtaining fermenting liquid whose viscosity is not less than 4500 cp, glue yield of greater than or equal to 1.9%, and reducing sugar of less than 0.1%; and (G) pre-treating the fermented fermenting liquid, extracting, washing, drying, cutting, and obtaining welan gum.