In this paper, an extended target tracking method based on the spatial structure characteristics of scattering centers is proposed for roadside radar surveillance. Current extended target tracking methods mainly track by taking the equivalent center after clustering as the target position or by establishing the target shape and size model. For the equivalent center method, with limited number of target scattering points, the result of clustering is not robust. For the establishing model method, it is difficult to achieve an effective high-precision target model and has a high computational cost when lack of prior information of the target shape. In this paper, the spatial structure characteristics of scattering centers are used to assist extended target tracking called the extended target scattering center (ET-SC) filter that is proposed. Compared with current extended target tracking methods, the proposed filter, which makes use of the spatial structure characteristics of scattering centers, has outstanding performance in estimation accuracy without a complex target model.