The parallel phase modulation (PPM) algorithm is investigated for spectral phase measurement and compensation. Detailed theoretical analysis and a numerical simulation are carried out to find how to determine the modulation frequency and reconstruct the spectral phase. A femtosecond pulse shaper is set up based on the PPM algorithm. The shaper is driven by our home-developed LabVIEW program and can be used to measure and compensate spectral phase of femtosecond pulses. The experimental results are verified with the multi-photon intra-pulse interference phase scan (MIIPS) method. Different from such existing ultrafast pulse measurement methods as MIIPS, the PPM method only needs to measure the signal intensity to determine the spectral phase quickly, and requires no spectrum measurements of nonlinear signals.