In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1;14mm.;I.D_2;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7~0.9$. The performance of heat exchanger was evaluated by using the $varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57~2.33$.