Multi-order cascaded Raman fiber lasers (CRFLs) are analyzed by an analytical method from optical power coupling equation under steady states used to describe stimulated Raman scattering (SRS). According to the parity of cascaded number, the output power is deduced, and the optimal length of Raman fiber and reflectivity of output-coupler are also obtained when the maximum pump-to-Stokes conversion efficiency is reached. The output characteristics and conversion efficiency as a function of Raman fiber length and output-coupler reflectivity of a 5th-order Ge-doped CRFL have been calculated with the residual pump power reflected into the input-end of resonant cavity being ignored. The comparison of calculated results and the experimental data for the 5th-order CRFL has been made.