The experiment of this paper is the thermal test of the leakage current of silicon PIN detector. Raising temperature may cause the detector to increase leakage current, decrease depletion and increase noise. Three samples are used in the experiment. One （called △E） is the sample of 100 μm in thickness. The other two （called E1 and E2） are stacks of five detectors of 1000 μm in thickness. All of them are 12 mm in diameter. The experiment has been done for 21 hours and with power on continuously. The samples have undergone more than 60 ℃ for about one hour. They are not degenerated when back to the room temperature. The depletion rate is temperature and bias voltage related. With the circuit of the experiment and temperature at 35 ℃, △E is still depleted while E1 and E2 are 94.9% and 99.7% depleted respectively. The noises of the samples can be derived from the values at room temperature and the thermal dependence of the leakage currents. With the addition of the noise of the pre-amplifier, the noises of E1, E2 and △E at 24 ℃ are 16.4, 16.3, and 10.5 keV （FWHM） respectively while at 35 ℃ are about 33.6, 33.1, and 20.6 keV （FWHM） respectively.
