A type of new conserved quantity of Mei symmetry for Appell equations in a holonomic system is investigated. Based on the definition and criterion of Mei symmetry for Appell equations in a holonomic system, a type of new structural equation and new conserved quantity of Mei symmetry for Appell equations in a holonomic system expressed by Appell function under the infinitesimal transformations of groups are obtained. An example is given to illustrate the application of the results.