Abstract: Fluid seal technology is one of the critical technologies in gas turbine design, which is used to reduce leakage and improve the efficiency of the gas turbine. Based on the traditional labyrinth seal (LS) structure, a series of seal fins with plenty of swirl slots are designed to divert and guide the interstage jet. Extra swirl slots can slow down the circumferential velocity of working gas to obtain a new type of seal with better rotordynamic characteristics, named slot labyrinth seal (SLS). The flow fields of the new structure and the traditional structure are calculated by Fluent. Rotordynamic characteristics and leakage performance of two types of seals are compared and analyzed. The following conclusions are obtained: the addition of SLS can significantly reduce the circumferential velocities of the working medium by 44.47% and 71.56% in the tip clearance and cavity, respectively. Compared with the traditional LS, the SLS can obtain about a 4.2% increase for direct stiffness and about a 33.4% decrease for cross-coupling stiffness. However, it will also increase the leakage by 3.2%. When the circumferential width of the slot width is 0.6 °, the depth is 6 mm, the axial deflection angle is 60°, and 16 slots are uniformly distributed in the circumferential direction, better dynamic characteristics and as low leakage as possible can be obtained.