In this paper , a new form conserved quantity of differential equations is presented. The conserved quantity is constructed only based on the general Lie group of transformation vector of the differential equations. The first-order and second-order differential equations are studied, respectively. Two theorems concing conservedquantities are proved. The relations between these theorems and preious conservation laws are discussed. A condition is given to exclude trivial conserved quantities. Finally, we give two examples to illustrate the application of the results.