[Abstract] Objective： The aim of the study was to investigate the change of nerve growth factor (NGF) in dorsal root ganglion innervating the heart in the early time of elevation of tail flick latency, i.e. formation of neuropathy in diabetic rats. Methods： Eighteen male Sprague-Dawley (SD) rats, weighing 200-250g, were randomly divided into control group (group C，n=6) and diabetic group （group DM, n=12）. Rats in DM group were given streptozotocin (STZ, 50mg/kg, i.p.). Tail flick test apparatus was used to measure the tail flick latency (TFL) of rats every week to monitor the development of diabetic neuropathy. The dorsal root ganglion（DRG）in upper thoracic segments (T1-5 ) innervating the heart and serum were collected when the diabetic animals presented significant elevation of TFL，compared to the age-matched non-diabetic control. The contents of NGF in the DRG and serum were evaluated using enzyme-linked immunosorbent assay. Results： The TFL significantly increased in diabetic rats in the 5th week after injection of STZ, compared with the values obtained from the age-matched non-diabetic rats in the control group（p<0.05）. Diabetic rats with lower increasing rates of TFL (less than 100%) were assigned to DM1 group (n=6) and the animals showing higher rates of elevation in TFL (greater than 100%) were defined as DM2 group (n=6). Interestingly, Compared with control groups, significant increases of NGF in the DRG and serum, by 18%（P<0.05）and 16%（P<0.05）respectively, were detected in DM1 group, while the levels of NGF in DM2 group were decreased by 40%（P<0.01）and 14%（P<0.05）, in the DRG and serum. Conclusion： The finding of this study suggest that with deterioration of diabetic neuropathy in the early stage of diabetic neuropathy, the NGF in the DRG innervating the heart and in the serum were up- and then down-regulated, of which the mechanism and biological significance were worthy to be further investigated.