To improve the performance of a micrometer inductive sensor, a design method of solenoid coils was put forward based on the theory of Helmholtz coils to improve the uniformity of the axial magnetic field of a solenoid coil. Firstly, the model of the solenoid coil was analyzed and the generalized function model between the parameter of solenoid coil and the axial magnetic field intensity distribution was established. Then, the system function model for axial magnetic field intensity distribution was determined based on the parameters of the core and coil sizes, the minimum error objective function of the uniformity for the magnetic field was set from the core moving range, and the best parameters of solenoid coil by objective function optimization were obtained. Finally, a test system for the micrometer inductive sensor was established to get its detection performance. The test results show that modified solenoid coil improves the linearity from 0.42% to 0.25% in 100 μm measurement range as compared with the original solenoid coil. It concludes that the modified solenoid coil uniforms the intensity distribution of the axial magnetic field and enhances the measurement accuracy.