Abstract: In order to analysis the electromagnetic railgun in-bore magnetic field distribution characteristic at zero speed, a two-dimensional railgun computational model is built. Based on the magnetic diffusion equation and Amperes law, the current density in each part of the rail and armature is obtained. Through the Biot and Savarts law, the magnetic flux density of the investigated point which locates in front of the armature is calculated, Based on the electromagnetic induction method, the magnetic field measurement experiments are carried out. The experimental values are in agreement with the calculation values. The results show that the magnitude of the magnetic field is determined by the current flowing through the armature and rails. To the investigated points in the central axis in front of the armature, the magnetic flux density decreases with the increase of the distance from the investigated point to armature, but the decay rate is gradually smaller. The results are helpful for the in-bore magnetic field shielding and intelligent ammunition design.