This paper studies the sedimentary facies, reservoir characteristics and seismic prediction of the Yijianfang Formation of Middle Ordovician in the Tuofutai area of Tahe oilfield. It is revealed that the depositional environment during the deposition of Yijianfang Formation in the studied area was an open marine platform facies, including intra-platform grain bank, interbank sea and patch reef subfacies. Main reservoir space was composed of intergrain pores, intergrain dissolved pores, fractures and caves with strong heterogeneity. Multiple dynamic parameters of seismic wave are used to directly demonstrate plane distribution of fracture-cave system.