Available transfer capability(ATC) is an important indicator of the usable amount of transmission capacity accessible by several parties for commercial trading in power transaction activities. This paper deals with an application of optimization technique for available transfer capability(ATC) calculation and analyzes the results of ATC by considering several constraints. Especially several optimization techniques are used to solve the ATC problem with state-steady security constraints. The results are compared with that of repeat power flow(RPF), sequential quadratic programming(SQP) and linear programming(LP). The proposed method is applied to 10 machines 39 buses model systems to show its effectiveness.