An improved phase retrieval method based on Hilbert transform is introduced to quantitatively calculate the phase distribution from a micro-interferometric pattern. The property of Hilbert transform, losing DC offsets and owning π/2 phase shifting, is used to remove the DC component and obtain the phase distribution from an off-axis interferogram. Compared with traditional Hilbert method, the Fourier transform is omitted that can avoid the questions of frequency leakage and improve the computational efficiency. Based on the micro-interferometric measurement, the improved method is used to retrieve the phase distribution of rabbit red blood cells. And the corresponding results show that it owns high calculation efficiency and the ability of reserving details of samples.