With the increasing concerns on the Free Floating Bike-Sharing (FFBS), the relationship between the usage of FFBS and built environment has been studied by many scholars. However, few studies have focused on specific urban areas such as the Central Business District (CBD), where the built environment features are unique. By taking Shenzhen, China as a case study, this study is aimed to explore how the built environment in CBD is associated with the FFBS usage. In order to understand the general usage pattern of FFBS in the CBD, FFBS usage is divided into three categories, FFBS origins, FFBS destinations and combined FFBS usage. The unique built environment features in CBD are categorized into building features, POI density and transport accessibility. The general usage pattern of FFBS in the CBD is first examined, which shows that CBD is more of a destination for FFBS usage than an origin. Then the study applied GWR model to discover the spatial variance of effect of built environment on FFBS usage. The results reveal that residence POI, workspace POI and metro accessibility are positively related to the arrives by FFBS. For the FFBS departing from the CBD area, unique characteristics of the CBD, such as high density of metro stations and the developed underground corridors, may be contributory determinants. The findings of this study can help to understand the usage pattern of FFBS and built environment determinants in the CBD, thereby contributing to rebalancing and relocating bikes in the CBD area for operators.