The invention discloses an ahead multi-layer speed fine modeling method based on polarization offset. The method comprises the steps of firstly distributing 16 three-component detectors and a shot point in one side of a tunnel, then receiving a three-component seismic signal of each detector via a seismograph, extracting a three-component reflection signal via tau-p transformation, and determiningthe number of reflection interface layers; determining the range of a speed v1 behind the first interface layer according to existing stratum data of tunnel construction, and selecting a position with maximum amplitude and length areas of previous and next periods for a first-layer reflection signal; detecting the areas in a gridding manner, selecting the different speed v1 values and wave groupzones to compute the polarization offset interface; at last, determining a first-layer actual speed through overlapping energy of common interface points, and determining the position and inclinationof the first interface according to a main polarization parameter; and then repeating the abovementioned process until speed models of all the reflection layers are built. According to the method, theactual speed of each stratum can be determined, and thus each accurate stratum speed model can be built.