A dual-parameter optical fiber sensor with a ball-fine core-ball structure is designed,and then the refractive index and axial strain characteristics of the optical fiber sensor are compared before and after the optical fiber is tapered.Through experimental and theoretical analysis,it is known that,after the fine core between the two-ball structure is drawn,it has a greater impact on the strain of the sensor and the sensitivity of the refractive index in the tapered area.The experimental structure is simple,convenient to manufacture and easy to repeat.After the tapering of the dual-parameter optical fiber sensor fabricated by this structure,the refractive index sensitivity of the tapered area is more than twice that of before the tapering,reaching 50.53 nm/RIU,and the axial strain sensitivity is also twice as high as that before the tapering.At about 2.908 pm/με,the experimental results are basically in line with the theoretical derivation.