Sealed coring is a special kind of coring operation. Through the cooperation of the sealed coring tool and the sealed coring bit， the core and drilling fluid can be isolated under the action of sealed fluid， and in-situ oil saturation and oil-water dynamic data can be obtained. The sealed coring bit is designed as a double channel structure， which can meet the requirements of drilling fluid flushing， cooling the bit lip and carrying cuttings. At the same time， the sealed fluid can form an enrichment area at the bottom hole to effectively protect the core from drilling fluid pollution. The channel parameters of the sealed coring bit are the key to the design of the sealed coring bit. Based on the theory of computational fluid dynamics， the k-epsilon turbulence model and continuity equation are used to simulate the two-phase flow field in the bottom hole of KM type sealed coring tool with the sealed coring impregnated diamond bit. The mixed flow state， fluid pressure， flow velocity and shear stress distribution characteristics of the bit lip are studied. The influence of flow characteristics on sealing effect， drilling efficiency and service life of the bit is analyzed， the design parameters of the channel structure of the sealed coring impregnated block diamond bit are verified， and the optimization design suggestions are put forward for the two-phase flow channel of the bit.