To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experimental setup. Fused fiber couplers optical performances such as insertion loss, excess loss, directivity and uniformity were tested with the optical test system that was constituted of tunable laser and optical spectrum analyzer. Especially the relationship between optical performance and drawing speed was investigated. The experimental results show that the optical performance is closely related to process conditions. At fused temperature of 1 200℃, there exists a drawing speed of 150 μm/s, which makes the devices performance optimum. Out of this speed region, the optical performance drops quickly. At drawing speed of 200 tm/s, the excess loss is relatively small when the fused temperature is above 1 200℃. So the technological parameters have close relationship with optical performance of the coupler, and the good performance coupler cant get until the drawing speed and fused temperature match accurately.