Abstract: The Noether symmetry and conserved quantity of generalized Chaplygin equations of nonholonomic system is studied. Firstly, a generalized Chaplygin form of d’ Alembert Lagrange principle is established. Secondly, the infinitesimal transformations of time and generalized coordinates are given and an invariance of the principle under the infinitesimal trarsformations is studied. Thirdly, the generalized Noether identity and corresponding conserved quantity are obtained. An example is finally given to illustrate the application of the result.