In phase-shift phase-measuring profilometry [1,2], an equivalent wavelength of the system could be defined as = P where p0 is the mean fringe pattern period at the reference plane, and e is the angle between the P. 0 direction of projection and the direction of observation. Increasing of equivalent wavelength leads to slowing down of the fringe phase variation. It would be benefit to phase unwrapping , but in the same time it leads to lower measurement accuracy. Here we present a new method. Considering both the reliability of phase unwrapping and the measurement accuracy of the system, we make two sets of fringes with different frequencies on a single grating pattern. Instead of using N (N=3,4,5 ...) phase steps, 2N phase steps is used. The phases of the two frequencies are calculated separately. It's possible to unwrap the high frequency phase, with reference to the low frequency phase.