A non-contact active scanning and structural grating projection positioning technique was used to reconstruct the three-dimensional point cloud data of combustion morphology of solid fuel ramjet grain after ground test using high density polyethylene (HDPE) as propellant. The three-dimensional distribution cloud map of mean local regression rate on the inner surface of solid fuel was obtained. The results showed that: (1) the error between the burning removal quality of the grain calculated by this method and the actual mass change after experiment was within 0.1%. The accuracy met the requirement of regression rate evaluation for solid fuel. (2) The reconstructed regression rate test method can truly reflect the change of fuel grain structure with certain applicability. (3) The relationship between mean local regression rate and total average regression rate was obtained by this method, and the relationship between regression rate and inflow air mass flux was obtained by linear fitting method. Through the validation and analysis of this method, it is concluded that the regression rate test method has a certain reference value for the further study of solid fuel ramjet gressionrate.