The invention discloses an in-site measurement system of an aspheric die. The system comprises a contact probe, an air-floatation bearing, an optical interference system, an image collecting and processing system and software processing system; the optical interference system comprises a light source, a laser beam expanding system, an cat eye reflector, two reflectors, a polarized spectroscope, a 1/2 lambda wave plate, three 1/4 lambda wave plates, a beam splitting grating or a holographic beam splitting unit, a space filter and a Polaroid group; the image collecting and processing system comprises a CCD camera, an image collection card and a computer; and the software processing system comprises a phase calculation module, a surface coordinate conversion module, a curved surface fitting module and an error analysis module. The system and methods thereof have the advantages that the displacement measuring precision can reach the nanometer magnitude, real-time in-site measurement can be realized, interference of vibration noises can be avoided in the measurement process, and the measuring accuracy and stability are high.