Ion-induced nucleation is a very important nucleation type, and it is also one of the main sources of new particles in atmosphere. It has a significant impact on the formation of new particles in atmosphere. By simulation of photoelectron and infrared spectroscopy of hydrated oxalate, it’s found that number of water molecules can affect the stability of cluster molecules. With respect to C2O2-4 (H2O)3 cluster, the addition of the fourth water molecule can effectively stabilize the two electrons with Coulomb repulsion on the oxalate molecule. The interaction between water molecules in oxalate hydrate clusters is weaker than that between water and oxalate molecule in hydrated. Simulation of infrared spectroscopy shows that the number of water molecules has less effect on the nuclear structure of oxalate.