In order to overcome the discontinous phase unwrapping problems existing in the shape measurement of the discontinuous objects, the spatial carrier grating fringe pattern produced by the computer of which the ratio of two frequencies is an irrational number, is introduced. By using the wavelet transform profilometry, the wrapped phase distribution corresponding to the two frequencies respectively in one bi-frequency grating pattern is got. And then applying the phase unwrapping by a lookup table method for unwrapping, the determinate modulated phase distribution corresponding to the two frequencies is got. The technique can tolerate the height discontinuity of the shape of the objects. The defailed theoretical deduction, experimental verification and an example of 3-D shape measurement are shown.