In order to explore the key human factors that lead to safety accidents in steel structure construction,this article collected 85 investigation reports on steel structure construction safety accidents in China. Based on this,a Human Factors Analysis and Classification System（HFACS）model suitable for steel structure construction safety accidents was constructed.In addition,the Analytic Hierarchy Process（AHP）is used to calculate the weights of risk factors in the constructed model,and to determine the key human factors that cause safety accidents in steel structure construction.The results showed that the key human factors causing steel structure construction safety accidents were the violation of operation by workers in S41,poor condition of workers in S31,skill errors of workers in S42,violation supervision in S22,and perception errors in S43 decisions.Finally,corresponding suggestions were proposed from the perspective of human factors to reduce the safety risks of steel structure construction.