This paper presents the queuing principle for staggered work hours and the methodology of congestion reduction in view of the policy for staggered work hours． The double-peaked phase theorem and the mixed phase theorem are formulated by extending the Vickrey’s bottleneck model in bi-arrival time and by introducing the concept of the staggered viscosity coefficient． The double-peaked phase theorem determines the sufficient and necessary conditions for the existence of the double-peaked or single-peaked queue． The proportion of travelers with mixed departure time for the two categories of travelers is resulted from the single-peaked queue in mixed phase theorem． Given the staggered time interval，the total queuing time or traffic congestion can be reduced by properly adjusting the ratio of the two categories of travelers． Given the volume of all travelers，the total queuing time keeps constant until the staggered time interval exceed a threshold． Three numerical examples are employed to demonstrate the principle and the related conclusions．