Abstract: Objective To evaluate the effect of free folic acid supplementation intervention on knowledge and behavior among pregnant women in rural areas of Gansu province.Methods A total of 1396 pregnant women were sampled with cluster random sampling, in which 410 pregnant women with history of folic acid supplemen tation were assigned as intervention group and 986 pregnant women without folic acid in tervention as control group.We collected information on knowledge and behavior about folic acid supplementation with a questionnaire survey.Results The awareness rate of folic acid, the use of folic acid for the prevention of neuraltube defect, and the best time to take folic acid was 99.02%,55.61%, and 38.78%, respectively, in the in tervention group and higher than those of in the control group(P < 0.05 for all).The rates of self reported use(95.37%), prescription(56.34%), and effective use(29.02%) of folic acid in the inter vention group were higher than those in the control group(P < 0.05 for all).The rate of effective compliance for folic acid use, partial effective compliance for folic acid use, ine ffective use rate of folic acid, and compliance rate for folic acid use was 16.34%, 8.05%, 31.22%, and 15.61%, respectively, in the intervention group and higher than those in the control group(P < 0.05 for a ll).Conclusion The intervention of free folic acid supplementation can improve pregnant womens knowledge and behavior abouttaking folic acid effectively in ruralareas of Gansu province.