In this paper, we introduce the main applications of matrix rank in linear algebra, the key content of which is to judge the reversibility of matrix, and to study the solutions of equations. We also discuss the conditions of linear correlation of vector group and the methods of judging whether the quadratic form is positive or not. We also introduce the applications of matrix rank in analytic geometry, In this paper, we mainly discuss the relation between the line and the plane position in the rank judgment space of matrix