The degree-constrained minimum spanning tree (DCMST) is an iVP-hard problem in graph theory. It consists of rinding a spanning tree whose vertices should not exceed some given maximum degrees and whose total edge length is minimal. In this paper, novel mathematical properties for DCMST are indicated which lead to a new reduction algorithm that can significantly reduce the size of the problem. Also an algorithm for DCMST to solve the smaller problem is presented which has been preprocessed by reduction algorithm.