Abstract: Since MATLAB can not write directly to hardware available for operation, and it lacks of the feature of real-time, the applications has been significantly hampered. MATLAB applications, through redeployment of C++ language interface Mex, can be achievable in the MATLAB environment for the specific hardware interface signals. Therefore, author of the paper explains in detail about Mex interfaces, including various special functions, and specific translation rules; enunciates the transfer and the use of Mex interface in the MATLAB environment. And in accordance with the relevant function of interface Mex, the design of MATLAB data acquisition system is discussed in theory for further extending the functions of MATLAB.