Due to their characteristics of a small luminous volume, high energy conversion efficiency, high stability, and coherence, laser-produced plasma extreme ultraviolet (LPP-EUV) light sources are widely used in the fields of advanced semiconductor manufacturing and inspection, material surface analysis, and EUV metrology. In this work, the emission spectrum diagnosis of a one μm solid-statelaser Sn plasma EUV light source was carried out. First, the 13.5 nm in-band radiation energy, the emission spectrum of the 7~24 nm EUV band, and the 350~750 nm visible light (VIS) band of 1 μm laser-excited solid Sn target plasma in vacuum under different laser peak power densities were measured. The energy conversion efficiency (CE) and spectral purity (SP) were calculated, and the influence of laser peak power density on EUV and VIS spectrum, CE, and SP of Sn plasma was analyzed. Within the parameter range of this experiment, CE increases rapidly at first and then decreases slowly with the increase in laser peak power density, reaching a maximum value of 2.47% at a laser peak power density of 5.2×10¹¹ W·cm^-2. SP increases with the increase of laser peak power density and reaches a maximum value of 7.52% at 1.5×10¹² W·cm^-2. Then, based on the time-resolved VIS spectrum of Sn plasma, the electron temperature (T_e) and electron density (n_e) from 60 to 160 ns after plasma initiation were calculated using the Saha-Boltzmann plot and Stark broadening method, and the temporal evolution of T_e and n_e of Snplasma in vacuum was studied. The influence of T_e and n_e on EUV band radiation and 13.5 nm in-band radiation was further analyzed. The results show that an increase in laser peak power density leads to an increase in plasmaT_e and n_e, and the changes in T_e and n_e affect the distribution of ions with different charge states, causing a change in the EUV radiation spectral distribution. Within the parameter range of this experiment, CE initially increases and then decreases with the increase of T_e and n_e, whereas SP continues to increase. A Te value that is too low will prevent the UTA peak of Sn plasma from reaching 13.5 nm, and a T_e value that is too high will cause more driving laser energy to be converted into EUV radiation below 13.5 nm, resulting in CE not reaching its optimal value. The above research results provide a research foundation and technical support for the engineering development of solid-state laser-driven LPP-EUV light source, as well as the independent development of EUV lithography, EUV metrology, and inspection in China.