The level characteristics of H2S molecular Rydberg series have been studied with the method of resonance enhanced multiphoton ionization spectroscopy (REMPI) in the range of 484~520 nm, in which the third harmonic output (355 nm) of a nanosecond pulsed Nd:YAG laser excited dye laser is used as excitation source. The result is that regular series include two sets of spectral peak series nested in the way that the spectral peak interval appears twice changes with the increase of the wavelength. It is clear that this spectral peak series corresponds to the Rydberg series. Based on low-lying excited electronic states and potential height Rydberg sequence, this ionization process has been confirmed five photons ionization (four and one). Now the strong spectral peak series has been assigned to the H2S molecule in concentrating to state np (n=5, 6, 7, 8) Rydberg series, and the weak spectral peak series has been assigned to the H2S molecule in concentrating to state ns (n=6, 7, 8) Rydberg series. Quantum losses of the two sequences are δ1=0.92 and δ2=1.52. The results are important to study the optical detection and spectroscopy characteristics of H2S molecules.