The kinematic of the rotor system is analyzed considering both universal joint structural misalignment and actual error misalignment.Firstly

the analytic expression about angular velocity fluctuation of the driven shaft is deduced based on coordinate transformation matrix.For presenting the harmonic relation between the angle velocity of the driven shaft and the driving shaft angle

the analytic expression is predigested three harmonic functions on θ under three different misalignment circumstances.At last

the theory relation between velocity fluctuation of driven shaft and driving shaft angle and the harmonic function fitting are calculated

verified

and compared each other.The research result can set the foundation for kinetic nonlinear restriction relation induced by universal joint

and is importance in the subsequent research of nonlinear oscillation of the misaligned rotor.