Employing the carbide interlayer between the substrate of cemented carbide and the diamond film is a preferred method of preparing the diamond coated tools for space drilling. In view of the issues such as interface coarsening and high heat stress resulting from high depositing temperature during chemical vapor deposition (CVD), this work attempts to deposit β-SiC interlayer at low temperature using mid-frequency magnetron sputtering, to discuss influence of the temperature on the organization structure of β-SiC interlayer, so as to reveal the mechanism of β-SiC interlayer to promote the nucleation and growth of diamond film on cemented carbide. The results show that: (1) in a temperature range of 100 oC - 400 oC adjusted in the mid-frequency magnetron sputtering, the β-SiC interlayer whose deposition temperature exceeds 300 oC is of higher compactness and crystallinity; (2) the β-SiC interlayer can restrain the catalytic effect of graphitization of Co binding phase in the substrate; (3) increasing β-SiC phase content has beneficial effect on the nucleation and growth of diamond film, and can improve adhesion of diamond film on the carbide. Based on the experimental data, the process of the nucleation and growth of diamond film on the β-SiC interlayer is explored, and a 6-step reaction model among atoms on the interface between β-SiC interlayer and diamond film is adopted to reveal the mechanism how β-SiC interlayer promotes the nucleation and growth of diamond film.