Abstract: The conformal invariance and Mei symmetry of the gradient system under infinitesimal transformations were considered. The author gave the definition and determining equations of Mei symmetry and Mei conserved quantity of the gradient system. The necessary and sufficient condition that conformal invariance of the gradient system would be Mei symmetry was given. Mei conserved quantity deduced from conformal invariance was obtained by making use of Mei symmetry.

Key words: Mei symmetry, conformal invariance, Mei conserved quantity, gradient system