Possible geometrical structures and relative stability of SimCn （m+n≤7） clusters are studied by using the hybrid density functional theory （B3LYP） with 6-31G*basis sets in this article. For the most stable isomers of SimCn （m+n≤7） clusters, the binding energy per atom （Eb）, second difference in energy （Δ2E） and HOMO-LUMO gaps （Eg） et al. are analyzed. The calculated results show that: with increasing of the number of atoms the structure of SiC binary clusters transform linear into planar, and then into a three-dimensional structure. When the atomic　number is less than 5, all clusters have planer structure except for Si5 and Si4C. With the increase of C atom, the average binding energy of SimCn （m+n≤7） clusters increases, which means that clusters of “rich C" are more stable than clusters of “rich Si", and Sin clusters with C doping can increase the stability. Cn, SiCn and Si2Cn clusters show clearly “odd-even" oscillation and the “magic number" effect, and Si2C,Si3C, Si5C,SiC2,Si3C2, Si4C2 and SiC4 clusters are more stable than other clusters.