As the current simulation methods for capillary burst valves can not exactly calculate the burst pressure when the passive valve is limited by a glass flat cover with good hydrophilicity,a method to analyze the critical pressure of the passive value was proposed. The Surface Evolver (SE) was used to simulate the burst pressure of the microvalve composed of a glass cover and PDMS microchannels by setting the properly boundary conditions and monitoring the variation of the contact angle at the entrance of expansion section.In simulation, the liquid contact line should be set up the entrance of expansion section and come into the expansionary walls that connect the glass cover. Experiments show that the capillary burst pressures are 0.77, 0.45, 0.33 and 0.24 kPa, respectively, for the microvalves with the depth of 25 μm and the aspect of 2, 4, 8 and 16. The obtained simulation data are well in agreement with that obtained by a rotating platform. The effect of the contact angle for the capillary burst valve was also discussed,which points out that the valves do work until the sum of the contact angles on both the flat cover and the channel wall is greater than 90°.