In order to study the effects of different packaging conditions on the residual thermal stresses of low temperature co-fired ceramic (LTCC) substrate after packaging and welding, the thermal stress deformation of LTCC substrate under different temperature variation loads were simulated and tested in this work. The results show that the simulation results are in good agreement with the experimental results, which verified the feasibility of the numerical simulation for simulating the residual thermal stress of LTCC substrate after packaging and welding. On this basis, the simulation calculation of LTCC substrates corresponding to three typical working temperatures under the condition of zero expansion alloy bottom plate and silicon aluminum alloy packaging are carried out. The results show that the stress of LTCC on both sides of the LTCC substrate edge is concentrated and the residual stress in the middle is small, showing a warped state, while the thermal stress with silicon aluminum alloy packaging and welding is less than that of the zero expansion alloy packaging.