The magnetic field uniformity on the axis of a straight solenoid wounded tightly with multilayers is improved by adding compensation coils. According to theoretical formula and combined with Python software,the magnetic induction curve before and after adding compensation coils is simulated. Based on the simulation results,the variation law between the improved uniform interval size of the magnetic field and the compensation coil parameters,the simulation curve graph is further studied. It is found that when the number of turns of the compensation coil is determined,the uniform interval size will increase first and then decrease with the increase of current intensity,and it will suddenly rise and drop when the convex points enter and exit the threshold of the curve graph. Under the premise that the current intensity can be provided,the compensation coil with fewer turns can produce better extension effect on the uniformity of the primary magnetic field.