The Lie-Mei symmetry and conserved quantities of Appell equation for a holonomic mechanical system are studied. On the basis of the Appell equation, we first obtain the Lie symmetry and the Mei symmetry for the equation and the conserved quantities deduced from them, then the definition and the criterion for Lie-Mei symmetry of Appell equation are presented. Lastly, the Mei conserved quantity and the Hojman conserved quantity are deduced from the Lie-Mei symmetry. An example is given to illustrate the application of the result.