Finite element analysis software was used to analyze the stress distribution of the original detector module and the detector module adding Kovar equilibrium layer. The simulation results showed that the thermal stress of the detector HgCdTe epitaxial layer decreased to some extent after adding the equilibrium layer， while the low-temperature warpage variable at the center of the detector chip surface decreased significantly. Without changing the material of the equilibrium layer， when the thickness of the equilibrium layer is 0.2 mm， 0.5 mm， 1 mm， 1.5 mm and 2 mm， the maximum stress on the HgCdTe chip first decreases greatly and then increases slightly with the increase of the thickness of the equilibrium layer. When the value of thickness is 1 mm， the maximum thermal stress on the detector chip is the lowest. Thermal stress level of large infrared detector chip can be improved by adding Kovar equilibrium layer.