Abstract: The large?scale application of steam assisted gravity drainage (SAGD) technology began in2012in Fengcheng oilfield. In order to ensure the circulation preheat performance, increase the horizontal section’s connecting degree and improve reservoir development efficiency, it is necessary to conduct the research of injection?production parameters optimization at the startup phase. In this paper, the objective function and the injection?production parameters of startup phase were confirmed by reservoir numerical simulation. Sensitivity analysis was done by compared simulation of“two goals and three factors”. The injection?production parameters optimization was then made according to their influencing results. Simulation results show that the high pressure and increasing temperature and the low steam consumption at startup phase should be adopted as follows: the preheat pressure is controlled by0.5~1.0MPa less than reservoir fracture pressure; the pressurization time is1~3days following uniform temperature in horizontal section; the steam injection rate reduces as much as possible in condition of horizontal section temperature equilibrium. The case study indicates that the optimization technology is practical and effective