Abstract: The spacecraft relative attitude solution is a precondition of the formation control and maintain. To address the problem of relative attitude solution for long-distance formation, the relative attitude determination method based on relative line-of-sight measurement was presented for multi-spacecraft formation. Considering the formation was composed of three spacecrafts, and each spacecraft was assumed to be equipped with vision sensors to measure the relative line-of-sight to the other two spacecrafts. Deterministic attitude solution algorithm was deduced and a mathematical simulation was carried out based on the visual sensor measurement model. Simulation results show that relative attitude solution method for multi-spacecraft formation can be used to estimate relative attitude between the spacecraft effectively and obtains a high accuracy. In addition, the method can meet the demand for spacecraft formation control and solves the limitation of visual sensor application for long-distance formation.