Characterized by a high resolution, high throughput (large effective area), and large field of view, the Wolter-I microscope is the main grazing incidence imaging device for x-rays and neutrons. It is necessary to estimate the tolerance of surface deformation to achieve the required resolution in typical applications. Traditional tolerance estimation method based on Monte Carlo method required a large random sampling in a given sampling area and has a low efficiency. We derived the transverse ray aberration equations to investigate the image quality degradation caused by principal figure and alignment errors and proposed a line fitting tolerance estimation method. Finally, the figure and alignment error tolerances of a Wolter-I microscope are discussed.