Summary: Structural equation and Mei conserved quantity of Mei symmetry for Appell equations in Chetaev nonholonomic systems are investigated. Appell equations and differential equations of motion for Chetaev nonholonomic mechanic systems are established. A expression of the total first derivative of the function with respect of time along the systematic motion track curve, and the definition and the criterion of Mei symmetry for Appell equations under the infinitesimal transformations of groups are also given. The expression of the structural equation and Mei conserved quantity for Mei symmetry in Appell is obtained. An example is given to illustrate the application of the results.