Abstract: A tbeoretical mddel of dynamic well control estabished in this paper is based on the assumption that a gas-mud two phase mixture is formed when gas flows into the well at kicking. The effects of gas slip velocity and frictional pressure drop in every flow pattern of two phase flow are taken into account.The finite difference method is used in solving mathematical equations and the algorithm of solving this numerical model is given. Two grid systems are built to overcome the difficulties in well control simulation. The effects of formation pressure, kick volume,size of annulus and pump flow rate on killing operation and on the maximum casing pressure are studied by computer simulation. Compared with experimental kill data,this model yields a closer result to actual case than that of a pumpout model.