The complexity of human brain activity has shown a certain law associated with the difference of age and sex, which can be identified by fMRI (functional magnetic resonance imaging). In this paper, we apply the base scale entropy to 54 groups’ fMRI data of different ages and gender, and then distinguish the different groups through the entropy. Through the base scale entropy with reasonable parameters, fMRI of different people could be distinguished effectively, which provides convenience to further data analysis. Results show that the base scale entropy between men and women of the same age has some differences and the entropy changes correspondingly with the change of age. In order to distinguish different people of different ages, we need to adjust the scale parameter to adapt to the trends in age changes. The fMRI data analysis shows that the base scale entropy could distinguish different populations’ fMRI data characteristics for further facilitating the analysis of complex signals.