Tip clearance of a coaxial rigid rotor is a key index related to helicopter safety. In this paper, an aeroelastic model for the coaxial rigid rotor was established, and the influences of various parameters on the tip clearance were carried out, including lateral lift offset, advance ratio, rotor crossover angle, control phase and high order harmonic aerodynamic loads. The results showed that the tip clearance decreases linearly with an increase in lift offset, and the larger the tension of the rotor is, the greater the decline rate of the tip clearance is. Moreover, the tip clearance does not decrease with the increasing flight speed, and the control phase and high order harmonic aerodynamic loads have little influence on tip clearance, but the rotor crossover angle has a certain effect on the tip clearance. Therefore, the lift offset is the most import parameter affecting the tip clearance, which indicates that the rotor tip clearance is mainly controlled by the flapping bending moment at blade root.