Abstract: Theoretical model to determine reasonable soaking time has been buih for steam stimulation well. It has been shown that steam injection parameters are the major effect to soaking time and remaining heat in previous cycle has little effect., the soaking time will prolong with the large amount of steam and high quality. Heated volume will be bigger for horizontal well and it has longer soaking time than vertical well under same injection condition. Reasonable soaking time are 3~5 days for vertical well and 5~7days for horizontal well for conventional injection state, it match field data.