The present disclosure discloses a method for estimating a channel error, comprising the following steps: performing range Fast Fourier Transformation (FFT) on data of respective channels to determine a cross-correlation function and a range frequency of the transformed data of respective channels along azimuth; determining a phase of the cross-correlation function and performing differentiation on the range frequency; and determining a linear change rate of the phase of the cross-correlation function with respect to the range frequency according to the phase of the cross-correlation function and the differential result of the range frequency, and taking the linear change rate as a delay error between respective channels. Meanwhile, the present disclosure discloses an apparatus for estimating a channel error. By using the technical solution for estimating and compensating the channel error according to the present disclosure, the channel error can be estimated precisely and stably, so that the imaging quality in applications such as SAR multi-beam imaging, interference imaging and moving target detection can be improved.