A multi-functional high-precision comprehensive diagnostic system for laser parameters was developed. The entire diagnostic system was composed of a fundamental frequency laser diagnostic module, a tripled frequency laser diagnostic module, an online optic damage inspection module, an opening frequency conversion unit and corresponding auxiliary units. Under the control of the system software, it can automatically perform accurate measurement, data collection, storage and processing on laser parameters such as near-field, far-field, energy, wavefront and pulse-waveform before and after the laser frequency conversion. This system provides accurate data for improving laser facility load capacity and researching relevant key unit technology.