Plutonium is vulnerable to aging due to α radioactive decay. The properties and behaviors of point defects in plutonium are the basis for understanding plutonium aging. We have employed a molecular dynamics technique to calculate the formation energy and binding energy of point defects and small helium-vacancy clusters in plutonium, using embedded atom method, Morse pair potential and the Lennard-Jones pair potential for describing the interactions of Pu-Pu, Pu-He and He-He, respectively. A single self-interstitial atom’s steady configuration is 〈100〉 dumb-bell. An interstitial helium atom at octahedral site is more stable than that at tetrahedral site. As a result of high binding energy of an interstitial helium atom to a vacancy, helium atoms can combine with vacancies to form helium-vacancy cluster during the process of self-radiation. The formation energy of helium-vacancy cluster increases with the increasing number of helium atoms. When the number of helium atoms equals to the number of vacancy, the helium-vacancy cluster is rather stable. Both substitutional and interstitial helium atoms are trapped at the grain boundary (GB). The binding energy of the self-interstitial atom at GB core is higher than that of helium atom and vacancy.