NOVELTY - Enhancing anaerobic fermentation of algal waste liquid to generate methane, comprises: adopting a centrifugation to extract extracellular polymeric substances of anaerobic sludge; mixing and adding the algal waste liquid and anaerobic sludge into an anaerobic bioreactor; adjusting the nutritive ratio of C/N/P in the anaerobic bioreactor; and after preheating, preparing the extracted extracellular polymeric substances and nickel chloride hexahydrate into mixed liquid A and adding the mixed liquid A into the anaerobic bioreactor.    USE - The method is useful for enhancing anaerobic fermentation of algal waste liquid to generate methane (claimed).    ADVANTAGE - The method has the advantages that necessary trace element nickel (Ni) for growing the methanogen is chelated into a dissolved-state biological promoter for utilization of the methanogen, the chemical precipitation action is overcome, the utilization ratio of the trace element is increased, the gas generation ratio for anaerobic fermentation of the algal waste liquid is increased to the maximum extent, the adding amount of the promoter is less, the cost is low and the operation is simple.    DETAILED DESCRIPTION - Enhancing anaerobic fermentation of algal waste liquid to generate methane, comprises: anaerobic centrifugation of sludge extracellular polymeric substances, taking mass concentration 8-9 g/L of anaerobic sludge mixture in 3000-3500 rpm centrifugal conditions for 10-15 minutes, the supernatant is discarded and the top-up with distilled water, twice; centrifuging again under the conditions of 3000-3500 rpm for 10-15 minutes, the supernatant is discarded directly after 10000-12000 rpm speed centrifugation under conditions for 10-15 minutes, taking supernatant after centrifugation through 0.22 mu m filter membrane extracellular polymeric substances can be obtained; extracellular polymeric organic matter content of 23-61%, protein content 2.1-28.3%, polysaccharides content of 1.0-23.0%, DNA content 0-5.2%; the waste algae mixed with anaerobic sludge is added to anaerobic reactor, the anaerobic sludge concentration of total amount of liquid attributable 8-9 g/L, and then adjusting the nutritive ratio of C/N/P in the anaerobic bioreactor, the specific method is: the use of methanol to change the ratio of organic carbon, the use of urea nitrogen ratio to change, where the inflowing water quality after the nutritive ratio is adjusted is as follows: chemical oxygen demand (COD) is 20000-25000 mg/L, C/N/P is (100-200):5:1, and pH value is 6.0-9.0, controlling anaerobic biological reactor temperature to 50-55 degrees C, the extracted extracellular polymer and the mass ratio of nickel chloride hexahydrate (NiCl2.6H2O) is 5:1 mixing ratio of 10:1 mixture A, preparing the extracted extracellular polymeric substances and nickel chloride hexahydrate into mixed liquid A and adding the mixed liquid A into the anaerobic bioreactor.