Abstract: In order to fill the need of high-performance scintillation probe for the current portable γ spectrometry, the CsI(Tl) crystal coupled with avalanche photo diode was adopted to constitute a new scintillation detector instead of NaI(Tl) crystal coupled with photomultiplier, also a low-noise charge sensitive amplifier was designed to serve as a readout circuit for the detector. For researching the performance of the improved scintillation probe, the regularity of the energy resolution changing with the temperature and the bias voltage was tested respectively based on the unique variable principle and experiments with spectrum response of γ ray for various radiation sources. The results show that the scintillation probe has a excellent characteristic of spectrum response for ¹³⁷Cs, ²²⁶Ra, ⁶⁰Co and ¹⁵²Eu sources when the temperature is 23 ℃ and the bias voltage is 370 V. Especially, the energy resolution is 4.98%, the SNR of the output signal is 21∶1 and the rise time is 80 ns for ¹³⁷Cs. Thus it can be seen that the improved scintillation probe, which has better energy resolution, smaller size and stronger performance of anti-mechanical and applicability, is significantly more excellent than the conventional one.