For the demanding of high precision optical system, a vertical Fizeau type interferometer, combining with dual-frequency laser displacement measuring interferometer, achieve submicron precision measurement of radius of curvature (ROC) in this article. In order to verify the credibility of the measurement system, a series of optical parts with different ROC are measured by two different reference transmission spherical respectively. Take the polished SiC sphere as an example, the main factors causing the measurement errors are analyzed in detail. Combining with the uncertainty theory, the uncertainties of the measurement results of ROC for SiC sphere is about 0.13 μm (a level of confidence of approximately 95% assuming a normal distribution), which demonstrate the measurement system meets the requirement of sub-micron accuracy measurement of ROC. The correctness of the final results measured is verified through the cross measurement of the same component by the coordinate measurement machine.