The invention discloses an optimization method of the parameter selection of key elements of a hydraulic electric compound hybrid power system, and belongs to the field of hybrid power. Number of population is set, operations of adaptive selection, intersecting and variation heredity and temperature reducing operation are carried out on the population, and the target value of an engine is confirmed. After certain algebraic simulated annealing genetic manipulation is carried out, and when an optimal adaptation degree and an average adaptation degree are small in difference, arithmetic is supposed to tend to be convergent in a given range, and adaptation degree evaluation is carried out on an optimal individual. If requirements are met, a loop is broken out, and otherwise, the optimal individual is used as a primary value of the system at the moment. The optimization method of the parameter selection of the key elements of the hydraulic electric compound hybrid power system improves the recovery rate of energy under the premise of meeting the power performance index, effectively recognizes the position of the optimal solution of the key elements, and improves whole performance of a vehicle.