Inverse synthetic aperture radar imaging is an important technique for radar detection and recognition of non-cooperative targets. However, for most of the existing imaging methods, pulse signals are transmitted and received at equal intervals, without considering the possible problems under condition of non-uniform data rate, such as accuracy decline of echo's range alignment and high side lobes in Doppler spectrum. The resulting vertical and horizontal defocusing can reduce the imaging quality and affect the feature extraction of the target. Therefore, an inverse synthetic aperture radar imaging method for non-uniform data rate is proposed. First, by designing the weight to simulate the alignment situation of uniform data rate, the correlation method with weighted sliding window is used to solve the problems of declined range alignment accuracy and vertical defocusing. Then, based on the linear form of non-uniform Fourier transform, the Fourier base matrix of non-uniform data rate is built, and CLEAN technology is used to complete the projection of echo signal on the bases iteratively. Finally, the Fourier basis matrix with uniform data rate is used to reconstruct the echo signal, which solves the problem of horizontal defocusing and makes the data rate of echo signal uniform. The effectiveness of the proposed method is verified by experiments using measured data.