The invention discloses a femtosecond optical frequency comb based sinusoidal phase modulation interferometric absolute distance measuring device and method. The device comprises a light source system, a sinusoidal phase modulation interferometric system and a signal processing system, wherein the light source system outputs two laser beams with different wavelengths, the laser beams are shot to the sinusoidal phase modulation interferometric system, the interferometric light beams are shot to the signal processing system for phase demodulation, and the distance to be measured is obtained according to frequency scanning interference and multi-wavelength interference principles; and the frequency scanning range in FSI (Frequency Scanning Interferometry) and the value of each wavelength in MWI (Multi-Wavelength Interferometry) are calibrated by a femtosecond optical frequency comb, and the distance measurement is directly traced to the time frequency standard. The device disclosed by theinvention is simple in optical path structure, large in measurement range, high in accuracy and capable of being applied to the fields such as large equipment manufacturing and precision metering.