The models of the straight through labyrinth seals with different geometry parameters were designed,The geometry parameters studied include seal clearance,fin number,fin pitch,fin height and fin tip thickness.The effect of geometry parameters on the sealing characteristics of the straight-through labyrinth seals were investigated numerically at different drop pressure ratios(the ratio of inlet and outlet pressure).The results show that the discharge coefficient is increased with the increasing of the drop pressure ratio,the seal clearance and the fin tip thickness,and decreased with the increasing of the fin height,the fin pitch and the fin number.The effect of seal clearance on the sealing characteristics is the maximum,the following is fin number,fin pitch,fin height and fin tip thickness.The correlation formula of discharge coefficient about these parameters was fitted by the method of least squares.The calculation results of the fitted formula are in good agreement with those obtained from numerical simulation,it can be used for the engineering design and calculation the labyrinth seals.