Ultraweak luminescence (UWL) is an universal phenomenon of photons emission in living organism. It is intrinsically connected with biological processes, and it closely links with biochemical, physiological and pathological conditions in organisms under stress. UWL testing is widely used in clinical medicine, agriculture, environmental protection and food industry etc. But it was not applied in testing physiological disease of agricultural product in storage. This study used tomato fruit as material to find rule of UWL in fruits under chilling stress, which is the main problem in tomato fruit storage. To obtain fruits with different chilling injury degree, before cold storage a group of fruits were treated with cold shock, the effective method to decrease chilling injury, which showed alleviative chilling injury symptom compared with untreated fruits. It was found that UWL rose with the degree of chilling injury, furthermore UWL went up remarkably (P＜0.01) before symptom of chilling injury happening. Correlation analysis between UWL and chilling injury rate and chilling injury index showed that correlation coefficient was 0.901 6 and 0.957 7(P＜0.01)respectively. In conclusion, UWL could factually reflect the degree of chilling injury.