T-Cell Protein Tyrosine Phosphatase (TCPTP, PTPN2) is a non-receptor type protein tyrosine phosphatase that is ubiquitously expressed in human cells. TCPTP is a critical component of a variety of key signaling pathways that are directly associated with the formation of cancer and inflammation. Thus, understanding the molecular mechanism of TCPTP activation and regulation is essential for the development of TCPTP therapeutics. Under basal conditions, TCPTP is largely inactive, although how this is achieved is poorly understood. Thus, in this study we used Intra and inter molecular CX-MS analysis to reveal molecular mechanism of TCPTP activity regulation, our both intra- and inter- molecular CX-MS analysis result shows that the C-terminal intrinsically disordered tail of TCPTP directly bind on the surface of catalytic domain and function as autoinhibitory element to control the TCPTP catalytic activity.