In order to improve the detection rate of dim targets in a single frame infrared image under low SNR conditions, and considering the characteristic that the high-order cumulant of Gaussian noise is zero and the statistical properties of the Gaussian process, a target detection algorithm based on third-order cumulant is proposed.Firstly, bilateral filtering is used to suppress the background, and then the gray value of the local neighborhood is used to construct the third-order cumulant, which is taken as the test statistic to divide the target point.Since the gray distribution of the target has the feature of rotation invariance, two rotation transformations are performed when constructing the third-order cumulant, which can further eliminate the influence of background clutter while enhancing the target energy, and reduce the false alarm rate of single frame detection.Experiments show that the third-order cumulant based on rotational transformation can effectively suppress edge clutter and detect dim targets with signal-to-noise ratio greater than 0.7.