Composite Packet in Multi-Wavelength Optical Packet Switching (MW-OPS) networks is studied to improve network efficiency by reducing non-transmission time. At the same time, long packets suffer higher packet loss rate in Fiber Delay Line (FDL) buffer under variable packet length environment. To further improve optical packet network performances, this paper proposes a composite packet system which tries to adjust packet length constant as well as to reduce the number of packet in optical domain. Improved performances are shown through computer simulations.