High residual stress that includes thermal and intrinsic stress is an obstacle to the further application of chemical vapor deposited diamond thick film. In this paper, CVD diamond thick film was deposited on silicon substrate by hot filament chemical vapor deposited (HFCVD) system. The finite element analysis (FEA) simulation and experimental research were carried out on the thermal and intrinsic stress of large area diamond thick film. The FEA model is set up to investigate the distribution and magnitude of thermal stress. The intrinsic stress is studied by X-Ray diffraction “sin2ψ” method. The thermal stress and intrinsic stress are both compression stress. Simulation results show the discontinuous sharp of the diamond film result in the stress concentration and low cooling velocity is a good way to reduce thermal stress. The intrinsic stress is correlative with the microstructure and non-diamond component of diamond film. The origin of the intrinsic stress is discussed in detail in this paper.