Objective To study on the factors of sheep plasma method detect heparin potency and improved methods.Methods Acorrding to sheep plasma method, to study the bubbles, solids, pH and NaCl concentration on the heparin potency determination.Results The bubbles impact on the heparin potency determination was less.Solids were the main factors on heparin potency determination, containing solids protein hydrolysates heparin potency determination was (2.87 ± 0.01 ) U/mL, after removing solids potency was 24.60 U/mL, raised about 8.5 times.In the removed solids sample, when pH 7.5 to 9.5 had little effect on heparin potency determination, and pH 6.5 and 7.0 had smaller effect on the heparin potency determination.The presence of solids in the sample, as the sample pH rised, heparin potency determination also rised, at potency of sample at pH 9.0 was 3.4 times than that at pH 6.5.Enzymatic hydrolyzate mainly contain: 47.86% protein, 39.16% NaCl, 4.12% fat, wherein the protein was 91.34% of small peptides.NaCl concentration had no effect on the heparin potency determination.The improved method of recovery assay value was 98.92%~101.53%.Conclusion The method is reliable, the heparin output value calculated by measuring value in accordance with the process of practical production output.This method can be used for the determination the production process of each link in heparin potency of heparin.