Abstract: The viewshed analysis is a terrain-based spatial-analysis method, which has been widely applied into both civil and military fields. However, in conventional methods, the propagation path of electromagnetic waves between the observation viewpoint and target point is generally modeled as straight lines. This consideration is inconsistent with the fact that the propagation path is curved due to the atmospheric refraction, leading to an inaccurate radar viewshed analysis result. To solve this issue, in this paper, a radar viewshed analysis algorithm that takes into account the atmospheric refraction and terrain shielding is proposed. In the algorithm, the equivalent earth radius factor is used to uniformly measure the impact of different atmospheric refraction on radar line-of-sight and terrain shielding. At the same time, the line-of-sight formula under different atmospheric refractions is applied to describe the propagation route of electromagnetic waves between the observation viewpoint and target point. Then, based on the propagation route and digital elevation data, the line-of-sight analysis between the observation point and target point is conducted. In this way, the algorithm obtains more accurate results of the viewshed of radar. Simulation calculations validate the effectiveness of the proposed algorithm and show that the proposed method has higher accuracy in radar viewshed calculation than traditional methods.