A novel compliant linear buffer mechanism (CLBM) is designed for impact isolation. In view of the incompatible relationship between frequency characteristic and parasitic error of compliant linear mechanism, the mixed compliant linear mechanism(MCLM) is proposed by combining the Lumped Compliant Mechanism(LCM) and the Distributed Compliant Mechanism(DCM).The topology matrices for four kinds of parallelogram linear compliant mechanisms are built through the method of type synthesis. The characteristic polynominal (CP) for the compliant mechanism matrices[CM] are calculated for the isomorphism detection of compliant mechanism. The finite element analysis (FEA) model of these four kinds of linear compliant mechanism is built to complete numerical analysis on the structure frequency and parasitic error with different sizes, and the relationship between the frequency characteristic and parasitic error of the compliant linear mechanism is found out. MatlabTM software is used to obtain the functional formulas by the method of polynomial curve fitting (PCF) for The FEA results show that the structure configuration of MCLM can achieve a higher structure frequency and a greater kinetic precision over the pure LCM and DCM at the same time, and also indicates that the analysis method of frequency characteristic and parasitic error for compliant mechanism is efficient and should be effective on the structure optimization of the novel CLBM.