Abstract: According to the BET formula, throuhgh static flow method, an instrument for measuring surface area of porous material was developed. This instrument has advantages of good performance, easy operation, wide suitability and inexpensive price. The principal, the basic structure, the characteristics of design and the operation of this instrument were described. Some experimental results, and compared them with those from other instrument was also provided. It was proved that the measurement of this instrument is precise and reliable.