Phase retrieval based on the transport-of-intensity equation is researched to calculate phase information from the intensity measurement. A practical phase retrieval system is designed including classic Fourier phase retrieval algorithm and phase retrieval algorithm based on the total variation. Only measurements of the spatial intensity of the optical wave in focal plane and defocus plane around are needed to retrieval the phase by solving a second-order differential equation. Phase retrieval based on the transport-of-intensity equation overcomes the disadvantages of iteration uncertainty and slow convergence compared with the iterative phase retrieval technique. The experimental results show that the phase retrieval based on the transport-of-intensity equation is able to quickly and effectively calculate phase information from the intensity measurement, and information in edge is remained at the same time of phase retrieval based on the total variation compared to Fourier algorithm.