The fiber reinforced thermoplastic composites(FRTC) was manufactured by using the conventional yarn covering method, and the mechanical characteristics were investigated. The viscosity characteristics of the matrixes to the temperature ranges were investigated by physics rheometer. The molding temperature ranges were determined with relation to the respective decomposition temperature ranges and the viscosity characteristics of the matrix materials. The results kom this work showed that the three-point flexural strength was increasedl but the damping ratios were decreased with press time and temperature increase. Certainly, the degree of impregnation was improved with temperature and pressure increased, but the unidirection of reinforced fibers was a little delomen for the increase of matrix flow. There was little difference in the distribution of reinforced fibers and the degree of impregnation between nylon-Kevlar29 composites molded at 26$0^{circ}C$ and PET-Kevlar29 composites molded at 275$^{circ}C$. This could be explained loom the almost same viscosity of nylon and PET at their respective molding temperatures. So, the viscosity was a very important factor in manufacturing fiber reinforced thermoplastic co- mposites(FRTC). It was possible to make fiber reinforced thermoplastic composites(FRTC) having the constant distribution of reinforced fibers and matrix volume fraction by the yarn covering method.