Abstract: Incomplete projection data was obtained by X-ray tangential detection of solid rocket motor. Superposition of defect information in X-ray film made judging work some difficult. In this paper, a method based on filter back projection algorithm was presented to reconstruct region of interesting in sectional view of solid rocket motor using the projection information of X-ray film. The simulation result showed that this method was effective for tangential defect especially the debonding in Solid Rocket Motor on the occasion of limited-angle and tangential detection.