The extreme ultraviolet (EUV) light conversion efficiency of the laser-produced tin plasma is closely related to the plasma characteristics. To diagnose the parameters of tin plasma, a Langmuir probe for laser-produced plasma diagnosis was designed. And the time evolution of electron temperature and electron density of tin plasma produced by different laser energies were studied. The results show that the peak electron density of the plasma is about 4.5×1011cm-3 with laser energy of 58.1mJ, and the maximum electron temperature is 16.5eV, which decreased with the reduction of laser energy. Moreover, the evolution trends of electron temperature measured by Langmuir probe and emission spectrometry are consistent. This study provides a new simple and rapid diagnostic method for laser-produced plasma EUV light source, which is beneficial to optimize the parameters of EUV light.