Chemical vapor deposition (CVD)-grown 2D materials like MoS2 and WS2 have been widely used for research and application. Here, we study substrates' effects on CVD-grown MoS2 and WS2. The morphology, crystalline quality and optical properties have been modified while changing substrates, which can be derived from lattice matching between 2D materials and substrate, defect/impurities on the interface and conductance/transparency of different substrates. The results provide suggestion for further study in CVD growth of 2D materials and device fabrications.