This study proposes a method for the accurate and real-time measurement of the angle between two planes based on the concentric circle mark and the principle of projective transformation. First, the curve equation corresponding to the concentric circle mark in the obtained image is fitted. Second, several vanishing points are calculated according to the invariant cross and harmonic ratios. The vanishing line equation of the plane, where the concentric circles are located, is fitted to determine the vanishing points of the two plane normals. Third, the angle between the two normals is calculated by combining known camera internal parameters. The angle between the two planes is the supplementary angle. The simulation results show that the method is feasible. The actual image experiments show that the absolute error is less than 1°, while the relative error is less than 1%. This method requires only the internal parameters of the camera and has no special requirements for the size of the concentric circle mark and shoot angle. Moreover, the method has high flexibility and can provide a convenient and efficient scheme for the space angle measurement.