Ti-6Al-4V alloy (TC4) is widely used in the field of marine and aviation, and its severe service environment is easy to lead to hydrogen embrittlement (HE) which can cause the degradation of mechanical properties and a sudden catastrophic fracture for the material. To investigate the HE behavior and mechanisms, mechanical properties of the TC4 alloy after different electrochemical hydrogen charging (EHC) time were measured by small punch test (SPT) first. Then, hydrogen distribution and the phase transition of the TC4 alloy with different EHC time were discussed in detail based on the atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The strength and elongation obtained by SPT fitting data show obvious deterioration with increasing EHC time while the macroscopic fracture morphology of the TC4 alloy exhibits a transformation from ductile mode to brittle mode. At the same time, the generation of hydride after EHC is proved a main contributor to the HE of the TC4 alloy. The results in this paper provide an effective and convenient method to assess the HE behavior of TC4 alloy in service.