Abstract: Enhancing damping characteristic is one of the effective methods to solve the instability problem of the rotor system. A three-dimensional numerical model of a scallop damper seal was established, and the multiple frequencies whirling method was used to solve the rotordynamic coefficients of the seal. The dynamic and leakage characteristics of the scallop damper seal, pocket damper seal and labyrinth seal were analyzed with/without inlet preswirls. Results show that the scallop damper seal’s circumferential baffle and the special structure of the scallop shape could reduce the circumferential velocity in the seal cavity, and improve the system stability. Without inlet preswirl, the direct damping coefficient and effective damping coefficient of the scallop damper seal are about 14.7% and 12.5% higher than that of the pocket damper seal, which is about 36 times and 17 times that of the labyrinth seal. The scallop damper seal has better dynamic stability, and the optimal interlaced angle of its cavity is 37.5°. With increasing inlet preswirl, the frequency dependence of the effective damping coefficient of the scallop damper seal and the pocket damper seal increases. The leakage flowrate of the scallop damper seal is slightly higher than that of the labyrinth seal, but lower than that of the pocket damper seal. Inlet preswirl slightly decreases the leakage flowrate of the scallop damper seal.