The invention relates to a sensitivity test system and method based on a wavelength phase shifting algorithm. Lasers emitted by a wavelength tuning laser are reflected back from a to-be-tested piece and a reference mirror in an optical path system and have interference, a CCD receives interference lasers returned from the to-be-tested piece and the reference mirror and records interference light intensity. The position of the reference mirror is adjusted by piezoelectric ceramic I according to hardware phase shifting principle, and surface form W1 of the to-be-tested piece is measured; surface form W2 of the to-be-tested piece is measured by changing wavelength according to the wavelength phase shifting algorithm. Interference cavity length when|W2-W1| is the minimum is determined. The position of the to-be-tested piece is adjusted by piezoelectric ceramic II, and the moving distance L of the piezoelectric ceramic II is recorded by a laser Doppler interferometer. Surface form W3 of the to-be-tested piece after the piezoelectric ceramic II moves for L is analyzed on the basis of the wavelength phase shifting algorithm, whether the difference between the surface forms W3 and W2 measured before and after adjustment of the piezoelectric ceramic II is consistent with the moving distance L of the piezoelectric ceramic II is analyzed, so that the wavelength phase shifting algorithm precision is obtained, and the purpose of calibration of measurement precision is achieved.