Kinematic accuracy is an important index to evaluate the quality of mechanisms. Kinematic reliability is a significant standard to examine dynamic kinematic accuracy of mechanisms. Having deduced inverse kinematics and calculated model for position errors of Delta mechanism, kinematic reliability of the mechanism is calculated considering the randomness of every error components. Analytic method sensitivity analysis is adopted to describe contribution of the randomness of each error component to kinematic reliability of the mechanism, and the calculating approach is exactly given that the sensitivity analysis which is for getting the error contributions to reliability of which the position errors during movement is in the range of allowable accuracy at any time. Kinematic reliability and its sensitivity analysis can search key factor influencing kinematic accuracy, which can provide the foundation for error compensate and accuracy assurance technology of the mechanism.