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The effect of stanchion and reverse flow on turbine power performance is studied based on Computational Fluid Dynamics (CFD). The turbine in this paper is developed by National Ocean Technology Center (NOTC), the experiment study has been carried out in year 2014. The simulation model is validated based on experimental results. The CFD model can simulate the marine current conditions up to an acceptable accuracy and is cost-effective compared with experimental work. The mesh dependent including prism layer cell mesh has been studied. There are two methods in simulating the turbine power performance which aer steady-state and transient model. We compared the results of these two methods, the difference of Cp was within 2% based on the same mesh size. The results of two methods showed little difference. We chose the steady-state method in the rest of the calculation to maintain the better economically computational model. The effect of different size of the rotating zone is calculated in the model. The results showed that the biggest gap is 1.06%, the size of rotation zone has little impact to the turbine performance. We simulated cylindrical stanchions with different distance against to turbine. Simulation model is established based on the validated model. The power coefficient curves were given based on simulation results. The results showed that the largest drop reached 25.3% between different distances. The effect of bi-directional flow to turbine power performance is studied through simulation model. The power decrease could reach 21.7% when the turbine is backward to the tidal flow is calculated and graphed. The numerical model established in this paper can simulate the performance of turbine well, The result can provide technical support for engineering application of tidal turbine.