The aim of this study is to investigate neural ensemble coding mechanisms via scoring firings in time window under fear conditioning. The original data were recorded at anterior cingulate cortex (ACC) of rats by implicated 16 channels array under two conditions: pre-training and testing. Then through a high-pass filtering (300 Hz-7.5 KHz), spike trains were obtained via spike sorting. Neural ensemble firings were scored in a selected window (30 ms) with a moving step (size of 1/4window). The score for the neural the ensemble was performed by counting spikes in the window based the maximum of spikes in the test case. The results show that the scores were lower in the pre-training where had no ensemble activity; in the test condition, the scores were higher, where presented ensemble activity. In pre-training, no ensemble activity was presented, which indicated that memory was not formed; in testing condition, obvious ensemble activity was manifested, which showed that the fear memory has been built up. Score coding method of neural ensemble were used to express different firing patterns of rats' ACC multicells in the different stages of fear conditioning trial, providing a support to explore the mechanism of synaptic plasticity of memory..