Abstract: Pack boronizing process was done on the surface of TC4(Ti-6Al-4V) alloy at 1000, 1050 and 1100°C, each was holding for 5, 10, 15 and 20h, separately. Then, the boronized layer thickness was tested and the curves of growing kinetics of the B-Ti compound layer were therefore given. Based on analyzing and fitting the test data with the software Sigma Plot 10.0, an isopach chart of boronzied layer was obtained. By XRD and SEM, the phase composition, microstructure and morphology of TC4 titanium alloy after boronizing were investigated. The results showed that the boronzied layer is composed of TiB2 and whiskerized TiB extending into matrix. Under such testing conditions, the layer thickness is in the range from 0.8 to 15μm. After a linear regression analysis, the average diffusive activation energy of boron in the TC4 titanium alloys is 65.23kJ/mol.