Aimed for the applications of χ(2):χ(2) cascaded second-order nonlinear phase shifts, it is theoretically proved that this nonlinear phase shifts can be measured by spectrally resolved two-beam coupling. The dependence of the cascaded nonlinear phase shifts on the phase mismatching in femtosecond time scald is investigated experimently. The proposed novel approach has advantages of high sensitivity and easy to be applied. The cascaded nonlinearities of weak χ(2) crystals can be measured easily by use of low energy femotosecond laser oscillators.