In order to research the calculation method of dynamic characteristic coefficients of sliding bearing and the relationship between different coordinate systems,two numerical analysis models of oil film pressure in polar coordinate system and rectangular coordinate system were established,in which the realization method of Reynolds boundary condition was presented.The formula of the perturbed pressure was derived using partial derivative method and the boundary condition was given.The transformation matrix of dynamic characteristic coefficients between two coordinate systems was discussed and verified.It is shown that the results of two models are consistent,which prove the method,thereby perfecting the classic bearing theory.