A method for characterizing the morphology property of ZnO film surface with Gaussian correlation is investigated. The parameters of root-mean-square roughness w and lateral correlation lengthξare introduced in Gaussian model to describe the correlation properties of the random film surfaces. In the experimental performance, ZnO thin films are grown on quartz glass and silicon substrates by the reactive radio-frequency magnetron sputtering method under different deposition pressure. The surface morphologies of the film surface are scanned by an atomic force microscopy. The height auto-correlation functions and root-mean-square roughness are obtained by using the numerical calculus method. Carried on the fitting with the Gaussian function to the height auto-correlation function data, the lateral correlation lengths are extracted to describe the statistical properties of ZnO thin film in mathematics with other parameters.