Abstract: Optical leak testing(OLT)is a new leak testing method for hermetic sealed devices.Under the certain lid stiffness and the volume of the package cavity,the minimum measurable equivalent standard leak rate of OLT is closely re-lated to the test time and the pressure of testing chamber.The relationship between the lid stiffness and the test time of OLT is discussed in this paper.The minimum test time to ensure the sufficient sensitivity of testing is studied with different cavity volume.