Abstract: The fluid-solid coupling model and calculation method of circumferential convergent hydrodynamic finger seal were established.Numerical simulation of fluid solid interaction was conducted in the process of rotor startup.The time-dependent change of leakage rate and radial force of interface was analyzed.Two parameters,i.e.:leakage rate and radial force of interface,were used to evaluate the performance of finger seal at stable state.These two parameters were calculated and their changes were analyzed in different working conditions and structure parameters of fluid interface.Research shows that leakage rate decreases rapidly and tends to be stable,radial force of interface reaches the maximum and then decreases to be stable at last in the process of rotor startup,meeting the requirements of low leakage and non-contacting finger seal.The work provides a basis for optimizing hydrodynamic finger seal with good performance.