Silica films were deposited on a silicon substrate by a plasma enhanced chemical vapor deposition method to study the stress variation and the refractive index distribution at different process conditions. The stress tester was used to measure the deformation of the wafer before and after coating, allowing the calculation of the film stress, and the prism coupler was used to measure the refractive index distribution. Under the same condition, when the flow ratio of SiH4 to N2O is set to 24, 27.6 and 30, the average refractive index of the film are 1.466 7, 1.459 2 and 1.455 7, respectively, at the wavelength of 1 539 nm, and the correspoonding compressive stress of the film are -50 MPa, -200 MPa, and -430 MPa, respectively. When the flow ratio of SiH4 to N2O is set to 22.6, 24, and 27.6 after minxing 8.3×10-7 m3/s GeH4, the average refractive indices are 1.4758, 1.4714 and 1.4633, respectively, and the corresponding wafer stresses are 25 MPa, -210 MPa and -270 MPa, respectively, which is a changing process from the tensile stress to the compressive stress. The result show that at the same flow ratio of SiH4 to N2O, GeH4 diffusion increases the refractive index and the compressive stress of the film. It turns out that with the reasonable selection of the process conditions, a refractive index stabilized silicon oxide waveguide film can be prepared, thereby improving the yield of the device over the entire wafer.