The invention relates to an interpolation algorithm for intensity-modulated radiation therapy plan dose data based on gradient features, belonging to the technical field of intensity-modulated radiation therapies. The interpolation algorithm comprises the following steps: obtaining various gradient edge points and non-gradient edge points on an intensity-modulated radiation therapy plan dose data plane by adopting an improved traditional Canny algorithm according to gradient features of the intensity-modulated radiation therapy plan dose data plane; obtaining a coefficient of a bicubic interpolation kernel corresponding to each point on the intensity-modulated radiation therapy plan dose data plane according to the acutance of a gradient profile corresponding to the obtained gradient edge points and the deviation coefficient corresponding to the non-gradient edge points; and performing bicubic interpolation of each point to be interpolated by using the coefficient of the bicubic interpolation kernel so as to obtain the intensity-modulated radiation therapy plan dose data of each point to be interpolated. The interpolation algorithm disclosed by the invention overcomes the smoothing effect of the traditional bilinear interpolation while the error is reduced; and the original gradient information is reserved.