To determine the spontaneous emission light spectrum (fluorescence lig ht spectrum) of microchip laser crystals at different temperatures,the output spectral characteristics of a microchip laser near the threshold are experimentally studied.In the experiments,when pump power is tuned slightl y less than laser threshold,the output light of microchip laser is after spontaneous emission light interference.Otherwise,when pump power is tuned larger than lase r threshold,the output light of microchip laser is laser light.The relationship of laser threshold and the crystal temperature of microchip l aser is measured.In the measurements,the laser threshold is increased with the increase of the crystal temperature,and the increasing rate is measured as 0.017W/℃ from 5℃ to 25℃.We also study t he envelope of spontaneous emission light spectra beneath the laser threshold wi th different crystal temperatures. The research results show the higher the temperature of laser crystal is,the l ower the spontaneous emission light spectral envelope peak is,and the decreasing rate is measured as 0.681%/℃ from 5℃ to 25℃.The red shift of the spontaneous emission light spectral envelope with increasing the temperatures of laser crystal was also observed,and the red-shift versus crystal temperature rate is measured as 3.1pm/℃ from 5℃ to 25℃.