Two tapered optical fibers, fabricated by nelt－pullingmethod, are assembled in some mode on two－dimension preciselymicrometer adjusting setting,which constitutes a new kind of fiber－op tic variable op tic attenuators(VOAs).Properties of transmitting are specialwhen light transmits in tapered fibers,which benefits light coup ling between two tapered fiber. The coup ling efficiency determines the power attenuation,which is important for a fiber－op tic VOA. Op tical fiber transmission and fiber coup ling between two tapered fibers are analyzed theoretically. Also, the coup ling efficiencies of two tapered fibers versus the vertical distance and the overlap length of two tapered regions of them are analyzed by experiment. All of those are important formanufacturing or studying fiber－op tic VOA.