Abstract: Many failure modes were found in mechanism motion and there is a correlation between different failure modes. In addition, numerical computation is hard to analyze and calculate the system motion reliability. To solve the problem, the correlation coefficients between different failure parameters are acquired according to the data from the simulation of motion reliability, thus giving the formulae of different method to solve the system reliability, including the joint probability density, bounded and conditional probability methods. Then, a comprehensive evaluation was carried out by any of the methods for the motion reliability of a mechanism, and the result showed that the system reliability thus calculated is more accurate in comparison to that calculated with parameters assumed separately.