The invention provides a method for removing annular artifacts of a flat panel detector. The method comprises the following steps: detecting non-responsive detection elements by utilizing a CT systemand recording the non-responsive detection elements into a defective pixel template; then respectively calculating the correlation coefficient of each probe response and the tube current, detecting the probe with the pixel value reaching the maximum value at the soonest, and recording the probe detected by the above method into a defective pixel template; taking a limited number of regions of interest in the dead-pixel-free region, and carrying out superposition averaging on the regions of interest to obtain a corresponding sinogram; with the sinogram of the region of interest adopted as a reference, fitting approximation is performed on the defective pixel region by using the B spline curve, so that a preliminary correction result can be obtained; and performing smoothing processing on the preliminary correction result by adopting an H-L consistency condition to obtain corrected output. According to the method, the annular artifact can be effectively removed. Only one fixed thresholdvalue is needed. The problem that in an existing dead pixel detection method, threshold value selection is difficult is solved. The method can be suitable for various types of detectors. The signal-to-noise ratio of the image can be improved.