Abstract: The mesoporous molecular sieve (SBA-15)/polydicyclopentadiene(PDCPD) composites were prepared by in-situ polymerization with SBA-15 supported catalyst (method 1), SBA-15 modified by coupling agent (method 2), modified SBA-15 supported catalyst (method 3), respectively. The effect of preparing methods on mechanical performances of SBA-15/PDCPD was investigated. The results show that for the SBA-15/PDCPD composites prepared by method 2, although modified SBA-15 can improve the interface interaction between SBA-15 and PDCPD matrix, the polymerization of dicyclopentadiene(DCPD) monomer is difficult to occur in the pores of SBA-15, causing the mechanical performances of composites improve weakly, compared with PDCPD. Method 1 and method 3 applied to prepare SBA-15/PDCPD composites are beneficial to the form of PDCPD molecular chains in the pores of SBA-15. The form of molecular chains in the pores can improve the interface interaction between SBA-15 and PDCPD matrix, enhancing the mechanical performances of composites greatly. Compared with PDCPD, the tensile strength and bending strength of SBA-15/PDCPD prepared by method 1 increase by 24.5% and 24% when the mass ratio of SBA-15/PDCPD is 2∶100, respectively. For the composites prepared by method 3, the quantity of PDCPD molecular chains formed in the pores of SBA-15 is smaller than that of method 1 due to the SBA-15 pores occupied by coupling agent molecule, resulting that the mechanical performances is lower than that of method 1, but higher than that of method 2.