In this work, the effect of pulsed magnetic treatment (PMT) on the microstructure of TC4 titanium alloy was investigated. TC4 titanium alloy is widely used in the manufacture of the blade of aviation engine. The microstructure of TC4 titanium alloy determines its property. PMT is a novel method used to modify the microstructures of alloys and has been explored in several papers recently. PMT has many advantages in the aspect of efficiency, energy-saving, non-deformation, etc. Therefore, the effect of PMT on the microstructures of TC4 titanium alloy was explored in this work. The variation of the dislocation density and the grain boundary angle of TC4 titanium alloy was observed after PMT. In the experiment, the magnetic induction density is 2 T, the pulse frequency is 5 Hz and the pulse number is 100. According to XRD tests, the dislocation density in TC4 alloy after PMT increased about 10.9%. KAM maps in EBSD test were used for evaluating the same area's dislocation density of the TC4 alloy before and after PMT. The dislocation distribution of TC4 titanium alloy changes notably: the in-grain dislocation density became more homogeneous and some local high-density areas disappeared, the distribution of dislocation near grain boundaries caused the angles of the grain boundaries altered and the fraction of low-angle grain boundaries decreased while the fraction of Σ11 grain boundaries (CSL grain boundary) increased. The motivation mechanism of the dislocation in TC4 titanium alloy under PMT was speculated based on the experimental results and some previous researches. The PMT may change the energy state of the electrons in pinning area of dislocations, which accelerates the electrons transformation from singlet state to triplet state and then increases the mobility of the vacancy or impurity atoms so that the dislocation de-pinning could occur under the original stress field and thus leads to dislocation movement and transformation of microstructure.