Abstract: The experiment of conversion efficiency of bolts tightening torque was carried out on site, the relation between installation torque and pre-tightening force was studied based on the different shapes, materials as well as damping filling modes. This experiment shows that: compared with the hexagon damping nuts, the nodular graphite nuts and the metal piece filling nuts respectively, the bolts with the square damping nuts, the malleable cast-iron nuts and the resin filling nuts require less installation torque to meet the equal pretension. Combining with the actual situation, the reasonable advices for improving the bolts pre-tightening force was given.