The invention belongs to the field of a numerically-controlled machine tool and relates to a numerically-controlled machine tool component importance analysis method. The method comprises the following steps: 1) establishing correspondence relation between components and fault time and between-component fault transfer relation; 2) carrying out analysis and establishing component transfer relation, and describing the numerically-controlled machine tool system component fault transfer relation through a matrix; 3) converting the fault transfer relation into a fault transfer hierarchy structure model, and determining the level of each system component in the fault transfer model; 4) carrying out numerically-controlled machine tool system component fault rate modeling based on time correlation; 5) calculating numerically-controlled machine tool system component fault correlation coefficient; 6) carrying out numerically-controlled machine tool system component fault rate modeling under fault rate correlation; and 7) establishing a numerically-controlled machine tool component reliability dynamic importance model and a core importance model, and carrying out component importance analysis. The method is more reasonable and practical compared with a conventional system component fault rate modeling method, which fails to give consideration to fault time correlation or fault propagation direction.