NOVELTY - Method for preparing bio organic fertilizer and complex microbial fertilizer involves (a) dehydrating potato waste residual liquid, solid material and liquid material, (b) stacking solid material (c) inoculating microbial inoculum, (d) turning heap, (e) detecting fermented material index and packing qualified product, (f) placing liquid material into liquid biological fermentation tank, (g) adding microbial inoculum, (h) heating liquid material and fermenting, (i) adding e.g. potash fertilizer, and (j) detecting fermented material index and packing product.    USE - The method is useful for preparing bio organic and complex microbial fertilizer (claimed).    ADVANTAGE - The method is cost-effective, and environmentally-friendly.    DETAILED DESCRIPTION - Method for preparing bio organic fertilizer and complex microbial fertilizer involves (a) dehydrating potato waste residual liquid to 82-88%, solid material to 60-65% and liquid material to 90-92%, (b) stacking solid material obtained in step (a) to 1.7 m width, and 0.8 m height, (c) inoculating aerobic fermentation microbial inoculum into stack of material in a weight ratio of 1000:1 and uniformly mixing, (d) turning the heap once at 60 degrees C for 3-4 days until the temperature is reduced to 30 degrees C, (e) detecting the fermented material index, where the material water content is reduced to below 30%, viable count of beneficial microorganisms is greater than or equal to 0.20000000/g, organic matter is greater than or equal to 30%, and pH is 5.5-8.5, qualifying the product and packing the qualified product, where the unqualified products are continuously fermented, (f) placing the liquid material obtained in step (a) into liquid biological fermentation tank, (g) adding fermentation microbial inoculum to the material in a weight ratio of 100:5, and uniformly stirring the mixture, (h) heating the liquid material in fermentation tank, and fermenting the mixture at 37-40 degrees C for 48 hours, (i) adding greater than or equal to 4% nitrogenous fertilizer, phosphatic fertilizer, and potash fertilizer, and uniformly stirring the mixture, and (j) detecting the fermented material index where the viable count of beneficial microorganisms is greater than or equal to 0.500000000/g (ml), qualifying the product to obtain complex fertilizer, packing the qualified complex fertilizer and continuously fermenting the non qualified product.