The geometrical structure, stability, electronic structure and magnetism of bimetallic clusters AuM2 and Au2M2, where M is 3d transition metal element, are investigated systematically by using the first-principles method based on density functional theory. In contrast to semiconductor clusters, the bimetallic clusters consisting of Au and transition metal elements usually form a large number of low-energy isomers, some of which are very similar in structure. Similar to the pure transition metal cluster, AuM2 and Au2M2 clusters also display dramatic magnetism. The magnetic moment of transition metal element in AuM2 and Au2M2 clusters is either enhanced or weakened with respect to the bulk value, which is closely dependent on the orbital splitting. For the ground state, the magnetic moments of two transition metal elements in AuCr2, Au2Cr2 and Au2Mn2 clusters are anti-parallel, and those in other clusters are parallel.