This paper proposes a new laser interferometer which is suitable for measuring the profile of an optical lens with a long focal length. Full-field heterodyne phase-shift technology is used to suppress the effects of factors such as vibration and the atmosphere on long-cavity interferometry. The heterodyne coherent measurement of the measured and reference wavefronts is achieved using a Twyman-Green interferometer structure. Experimental equipment is developed, and an experiment is conducted to prove that the novel setup can suppress the influences of external vibration and atmospheric turbulence on the measurement accuracy,achieving a long-cavity measurement with a root mean square repeated measurement accuracy of 0.45‰λ. Thus, this technology can prove to be a valuable alternative to traditional long-cavity interferometry.