Abstract: Numerical simulation technique is used to study the influences of lithologic interbeds and non--lithologic interbeds (single or multiple) on development effects of horizontal fracture assisted steamflooding in heavy oil reservoirs. Simulation results show that the existence of interbeds in reservoirs is not necessarily an unfavorable factor; different penetration in steam injection wells have different effects on production of this kind of reservoirs, penetration in steam injection wells is determined according to the types and distribution of interbeds.