Conformal invarianee and conserved quantities of general holonomic systems are studied. A one-parameter infinitesimal transformation group and its infinitesimal transformation vector of generators are described.The definition of conformal invariance and determining equation for the system are provided.The conformal factor expression is deduced from conformal invariance and Lie symmetry.The necessary and sufficient condition,that conformal invariance of the system would be Lie symmetry,is obtained under the infinitesimal one-parameter transformation group. The corresponding conserved quantity is derived with the aid of a structure equation.Lastly,an example is given to demonstrate the application of the result.