The first discovered heavy fermion superconductor CeCu2Si2 had been believed to have d-wave pairing symmetry for many years. However, recent experiments on CeCu2Si2 discovered behaviors consistent with non-nodal superconducting gap at very low temperatures. We have prepared high quality single crystals of CeCu2Si2 and proposed to perform ZF and TF MuSR experiments to clarify the superconducting gap symmetry.