For unconstrained optimization problems, the improved HS three-term conjugate gradient method is approximated by the two-term conjugate gradient method DL method, and the improved DL conjugate gradient method MDL conjugate gradient method is proposed. Compared with DL conjugate gradient method, this method has a better property, that is, the search direction of the conjugate gradient method can satisfy sufficient descent condition without relying on any line search. It is theoretically proved that the method has global convergence for general functions under Wolfe line search condition.