Hydraulic condition for alternate-bar formation in open channel flows with suspended sediment are determined by stability, analysis. It is shown that the condition for alternate bar formation in the flow with suspended sediment is much different from in the flow without suspended sediment. The theory demonstrate the effect of suspended sediment on the formation of alternate bars. When bed load and suspended load are present, the value of the neutrally stable stage is stable for the bed load only case and unstable for the suspended load only case. Thus, the two modes of transport produce opposite effects and the region where they balance identifies the neutrally stable case.