Objective To detect the level of IL-10 and IL-21 in serum of patients with psoriasis and explore its significance of judge the extent of serious condition and treatment of psoriasis.Methods According to clinical dermatology edited by Zhao Bian diagnostic criteria,selected 65 cases of patients with psoriasis during the period from March to September in 2014 ad-mitted to Department of Dermatology of out-patient and hospitalization.25 cases were progressive stage (group A),20 pa-tients with stable stage (group B),20 patients were in recovery period (group C),and 25 cases of control group (group D). With ELISA method detect the expression level of IL-10 and IL-21 in serum of each group respectively.PASI score will take to all psoriasis patients meanwhile.Results The expressionlevels of IL-21 in serum of A (127.59 ± 16.09 pg/ml),B (105.74±21.08 pg/ml)two groups were significantly higher than that in D group (85.46±14.25 pg/ml),and the differ-ence were statistically significant (t=5.174,4.863,both P <0.01),while the expression levels of IL-10 in A (10.64±3.23 pg/ml)and B (12.27±2.18 pg/ml)were both lower than D group (20.29±2.51 pg/ml),and the difference were statisti-cally significant (t=2.031,2.027,both P <0.05).The expression of IL-21 (94.03±8.90 pg/ml)in C group was higher than that in D group,and the difference was statistically significant (t=2.033,P <0.05).The level of IL-21 in A group was higher than that in group C,and the difference was statistically significant (t=2.352,P <0.05),while the expression level of IL-10 was lower than that in C group (19.69±1.54 pg/ml),and the difference was statistically significant (t=2.071,P<0.05).The expression level of IL-21 in the serum of patients with psoriasis and PASI score was positively correlated (r=0.508,P =0.027),while the expression level of IL-10 and PASI score was negatively correlated (r=-0.413,P =0.039). Conclusion The progression of psoriasis is related to the increasion of IL-21 or the decreasion of IL-10.The detection of IL-21 and IL-10 was beneficial to judge the severity and efficacy evaluation of psoriasis.