Abstract: Channel siltation is the key point which affects the working for the high-silt conveyance channel in irrigation area. This paper takes the siltation calculation of the secondary channel of An-Jihai reservoir in Xinjiang Ba-Yin river as an example. According to the theoretical calculation results of sediment threshold velocity and water flow velocity, sediment discharge of bed load and silt carrying capacity, the cause of silt deposition of high-silt laden conveyance channel was analyzed from different aspects. The results of theoretical calculation indicate that water flow velocity should not only be considered that it is greater than competent velocity in designing channel, its transport capacity should also be checked according to the minimal slope of channel when the slope of channel changes along the length to prevent channel from silting. To verify the accuracy of the above calculation, the prototype observation experiment was carried out. The results show that theoretical calculation result accords with prototype observation, and the theory calculation process of channel is rational and reliable, which can provide some important references for engineering design and management units.