Fiber taper is an important technology in optical fiber device manufacture. In order to research the relationship between the taper wasit shape and the taper parameters in the fast reciprocating moving hot-zone fused taper system, a theoretical model of the reciprocating moving hot-zone fused taper system is established based on the principle of volume invariance under the condition that the hot-zone moving speed is greater than the fiber tapering speed. The deformation processing of the tapered optical fiber is depicted in detail. Quantitative relationships between the diameter of the taper waist, the length of the taper waist and the moving number of the hot-zone, the moving speed of the hot-zone, tapering speed of the fiber, the reciprocating moving distance of the hot-zone, the width of the hot-zone and the initial optical fiber diameter are deduced in this paper. Experiments are also carried out to verify the validity of the proposed theory and the experimental results have good agreement with the theory.