A comprehensive model and method to on-line compute total transfer capability in power systems is proposed. The definition of the power transfer is given based on the generation scheduling and short term load forecasting. The proposed model handles the static security constraints such as the voltage limits and the branch loading limits, the steady state stability constraints and the transient stability constraints all together with a credible contingency list. A static continuation power flow method with the transient stability constraints is proposed to solve this problem. It combined the effectiveness of handling the static constraints of CPF with the effectiveness of handling the transient constraints of the fast time-domain simulation technique. Case studies with a practical power system indicate that the proposed model and method are effective and suitable for on-line application in a large scale power system.