“…A series of instruments developed by Professor Takeshi Kikutani form Tokyo Institute of Technology,are used to realize online measurement of diameter, temperature, velocity, orientation and based on which the use of PET during high speed spinning is studied [1] . Numerical simulation of spinning dynamics is researched in studying spinning dynamics formerly [2][3][4] , but there is a certain error between simulated result and the actual situation because of the difficulties which exist in the process of establishment of polymer model, determination of boundary condition and numerical calculation.Therefore, it is very important to study the equipment of the online diameter measurement for fiber spinning, which is very meaningful for realizing the high speed data acquisition, avoiding artificially error, protecting the quality of production efficiently and realizing the automatically collect information in the progress of the manufacture. The computer interface of the equipment is USB, which is of plug and play, high speed transmission, good scalability, easy using etc.…”