Abstract: Aiming at rigid blocks with a certain thickness, a scaling rigid block matching method was proposed to solve the problems of rigid transformation and scale transformation in block matching process. At first, the surface of each block was segmented by an improved region growing algorithm, and the fracture surfaces of the block were extracted according to its roughness. Then, an improved iterative closest point (ICP) algorithm was proposed by integrating scale matrix, rotation angle constraint and active iterative coefficient to ICP algorithm. Finally, the improved ICP algorithm was used to complete fracture surfaces matching of rigid blocks. The experimental results show that, compared with ICP algorithm, the improved ICP algorithm can overcome the problem of scaling transformation; And compared with scaling ICP (SICP) algorithm, the improved ICP algorithm can get much higher accuracy and convergence rate in fracture surface matching process.