The relations between two highly clustered scale-free network evolution mechanisms and synchronizability are studied in this paper. Firstly, we propose an extended Holme and Kim (EHK) model with adjustive clustering coefficients and power-law exponent based on the Holme and Kim (HK) model. Triad formation mechanism is extended among old nodes compared with the HK model. And the following shortages of HK modle are settled: there is no link evolution in old nodes and the numbers of links of a new node adding to network is fixed. Secondly, the effect of triad formation on synchronizability in an unweighted network is investigated. Finally, simulation results show that the triad formation mechanism can weaken the synchronizability of both types of networks.