The structures and properties(geometrical optimization,molecular vibration,thermodynamics,activation of reaction and stability) of furazan and its radicals are studied theoretically by using DMol³. The calculated results show that there are weak conjugated effects on rings of furazan and its radicals,the N—O bonds are the weakest on rings; the order of molecular stability is furazan＞single-radical＞double-radical; the rings have a certain ability to accept electrons from H atoms which connect with them and become more stable consequently; the double-radical has some electrophilic,nucleophilic and radical ability,single-radical takes the second place and furazan is the most inertial; N atoms on all molecules probably have certain activations of reactions.