Separation and collision between the vane and piston of a variable-speed compressor increases internal leakage and has periodic effects. To understand the dynamic characteristics of the vane–piston separation–collision process, a platform was established to experimentally observe the vane motion, and the process and details of the vane motion were observed using high-speed photography and precision image-processing technologies. The results showed the occurrence of vane–piston separation–collision. A mathematical model of the vane–piston separation–collision process was established based on Lagrange's equations and the kinematic CoR, and this was verified experimentally. The characteristics and influencing factors of the separation–collision process were analyzed using the mathematical model. The results showed that the vane has different dynamic characteristics under different operating conditions. The separation–collision process is closely related to k and N.As k is increased, it becomes more difficult for the vane to separate from the piston. As N is increased, it becomes easier for the vane to separate from the piston. Our results provide experimental and theoretical input for how to prevent vane-piston separation in this type of variable-speed compressors.A mathematical model of the vane–piston separation–collision process was established based on Lagrange's equations and the kinematic CoR