Abstract: Sealing performance is an important parameter for the evaluation on connection performance of tubing and casing connections.It has important influences on production safety and environment in oil and gas well.Based on the author's previous research,calculation expression of tightening torque on tubing and casing connection with shoulder face in make-up condition is established by analyzing load and friction and referring relevant literatures.Experimental rig is set up to test the sealing performance of tubing and casing connection.The influences of tightening torque,sealing gas pressure,initial seal clearance and the roughness of shoulder surface on the leakage rate are investigated.And some concrete variation curves are obtained and analyzed in detail.