The dynamic behavior of a clearance‐type mechanical seal is investigated. Five degrees of freedom are considered for its motion. The seal is used for a fixed rotor with a floating stator. For small oscillation it is shown that the axial motion is not coupled with the other modes, two for radial modes and the remaining two for angular modes. The axial motion in this situation is always stable. The design variables are grouped to form five meaningful dimension‐less parameters. Based on these parameters, the condition for stable seal motion is presented with the Routh stability criterion. It is found that the major factors affecting the seal stability are the ring dimension, the inertia capacity and the load capacity. The dynamic response of the seal ring is also presented by solving the nonlinear equations for five degrees of freedom.