Galling failure problem is always the key factor that can affect the safety and working life in oil pipe threaded connection. This paper establishes an experimental equipment that can simulate the contact of threaded connection. Taking P110S oil pipe threaded connection as an example, the variation process on thread surface with different load and friction is observed and the influence of contact stress on galling failure is analyzed. Applying the practical tightening contact stress on the thread surface, the surface topography with galling failure is observed. When the contact stress is 300 MPa, after making up and breaking out four times, galling failure will happen on P110S oil pipe threaded connection. This number is identical to the practical usage number in industry.