Two types of conserved quantities deduced by Lie-Mei symmetry of variable mass mechanical system are studied in phase space in the paper. The definition and criterion of Lie-Mei symmetry for the system are given. A coordination function is introduced，and the conditions under which the Lie-Mei symmetry leads to the two types of conserved quantities and the forms of the two types of conserved quantities are obtained. An illustrative example is given. The coordination function can be selected according to the requirement for finding the gauge function，and the choice of the coordination function is multiformal，so more conserved quantities can be deduced from Lie-Mei symmetry of the system.