Abstract: For composite material structure bolt connection, different operating conditions will change the friction coefficient between the bearing surface and the thread, thus affecting the torque coefficient, which makes the changing trend of the clamping force with tightening torque very complicated. Firstly, the theoretical analysis of the bolt tightening process was made and the express formulas of the clamping force and the bolt yield clamping force under the state of combined stress were obtained. Then, taking a certain type of bolt as the object for experimental research, under the specified target clamping force, the tightening curves under different operating conditions of lubrication, washer, and tightening speed were tested respectively. The test results show that, different lubrication conditions, washer conditions and tightening speeds have certain influences on the dispersion of clamping force and tightening torque curves, the tightening torque required when the clamping force reaches the same size, and the changing trend of clamping force with tightening torque. By studying the clamping force during bolt tightening process under the above operating conditions, it can provide some reference and basis for the precision of bolt connection structure and process design in composite material components.