Abstract: During the casing running for cementing, the bottom hole pressure (BHP) balance is closely related to the surge pressure.The casing running speed is a major factor influencing the surge pressure. Therefore, it is essential for safe cementing to ascertain a rational casing running speed. Depending on the casing running conditions, and based on the advanced four-parameter rheological model, a narrow trough model was adopted to obtain the annular flow rate in accordance with the fluid flow continuity in wellbore and corresponding boundary conditions. Then, supposing the obtained flow rate is equal to the flow rate obtained from conventional model,a model for computing the maximal safe casing running speed was established. The verification results show that the safe casing running speed obtained by the model only has a less than 10% error to that measured in an actual well. This indicates that the computation model is accurate to certain extent, and it can provide references for the casing running operation on site.