Analysis of BTA deep hole drilling bar on Liquid-Solid Coupled Vibration model, there are vortex and unstability on bending deformation of the rotating boring drilling bar induced by cutting fluid force. At first, the rotating fluid force inside the boring bar was expressed linear physical form, and it’s stiffness and damping coefficients were derived by the unsteady reynolds dynamic equation of the fluid. Then establish conditions including eddy and mechanical mechanism of the boring bar by cutting fluid force. The results of analysis show that the solution on coupled vibration model are more accurate than the other vibration model. Coriolis effect is the main reason for eddy or unstability of the deep hole boring bar induced by cutting fluid internal the drilling bar’s wall. Some rules are also derived with which cutting parameters can be selected reasonably, which is coincide with the parameters used in heavy machine building industry.