Waveband switching can effectively red uce the switching port number of wavelengths.The waveband value choosing algorit h m for the circumstance when the traffics between network nodes are known is stud ied in this paper.A waveband choosing algorithm based on k-mea ns named KWC is propose d.This scheme divides traffics into groups.Similar traffics belong to the same g roup and are carried by the sa me granular waveband to improve the waveband utilization.The simulation results show that KWC algorithm uses les s wavebands and has less idle wavelengths than other schemes studied in this paper when traffic grooming is no t used.The performance of different waveband choosing algorithms is also compared when static waveband tr affic grooming is used.A new traffic filling scheme is proposed for the multi-granular waveband system.Diff erent traffic filling schemes are used according to waveband granularity to decrease the waveband number and impro ve waveband utilization.For larger granular waveband,downward traffic filling is used.For smaller granular w aveband,upward traffic filling is used.The simulation results show that KWC algorithm can effectively reduce the waveband number and increase the waveband utilization compared with other schemes when traffic grooming is us ed.The combination of KWC algorithm and static waveband grooming algorithm based on multicast routing can make the waveband utilization above 98%.