Failure Mode and Effects and Criticality Analysis(FMECA) of timing system in SG-III prototype is developed in order to improve the reliability of time system in Inertial Confinement Fusion(ICF) facility. This work effectively analyzes the most severe faults, concludes the disadvantages of the timing system, and puts forward improvement methods. The experimental results show that FMECA has successfully improved the reliability of the timing system, enabling the mean shot between failures above 1 256 shots. This work can provide a feasible and effective method for studying on the reliability of laser facility for ICF.