<p>The kinematic failure of mechanisms is mostly caused by the input uncertainties that exist in the components. This work presents a reliability sensitivity analysis, including parametric reliability sensitivity (PRS) and global reliability sensitivity (GRS), to identify the main source of mechanism failure. Based on the interval process of motion error, a time-dependent reliability index is introduced to evaluate the reliability of mechanisms with interval inputs. The PRS is derived as the partial derivatives of the time-dependent reliability index with respect to the parameters of the interval inputs. The GRS is defined as the individual contribution of each interval input or the interactive contribution among multiple interval inputs to the time-dependent reliability index. Both the PRS and GRS are tested with two numerical examples and applied to the engineering application of an aircraft thrust reverser mechanism. The results show that the PRS and GRS analyses provide an effective tool for screening important inputs, which can be useful for reliability-based design optimization.</p>