Helium was introduced into ZrCo and Zr_0.7Hf_0.3Co alloys by mixed energy ion implantation. The evolution of helium bubble morphology with storage time was observed by Transmission Electron Microscope (TEM). Results showed that the average size of helium bubbles in Zr_0.7Hf_0.3Co alloy was smaller than that of ZrCo and both of them were observed in the coalescence and growth of helium bubbles with storage time increasing. The effect of storage time on the thermal helium desorption behavior was investigated by Thermal Desorption Spectroscopy (TDS). Results showed that in ZrCo alloy the helium release fraction at lower temperature range decreased sharply and the total helium desorption capacity decreased with the storage time reaching 105 days. While in the case of Zr_0.7Hf_0.3Co, the helium release fraction at lower temperature range gradually increased and the total desorption capacity of helium was almost constant during the storage period of 175 days. This indicated that Zr_0.7Hf_0.3Co alloy had more superior ability to contain helium than ZrCo alloy.