As one of the most promising optoelectronic materials in recent years, colloidal all-inorganic lead halide perovskite nanocrystals (NCs) have become a research focus. An in-depth understanding of electron behavior in the material is essential for advanced device application. Here, temperature-dependent photoluminescence (PL) spectroscopy is employed to study the optical properties of CsPbBr NCs film. It is found that the PL intensity decreased with temperature below 200 K, while reverse trend has been observed with temperature above 200 K. The mechanism of the PL unusual quenching phenomenon is attributed to surface states of NCs, which leads to non-radiative recombination of electrons at low temperatures. Above the critical temperature, electrons will escape from the defect level and participate in radiative recombination, which give rise to the enhanced emission. The model is further verified by comparison with nanoplatelets, surface passivation, as well as temperature-dependent PL decay experiments.