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Based on the variable slopes flume experiment, adopting ultrasonic measurement technique, changes in hydraulic parameters of slope shallow flow were studied at five slopes and 21 unit width discharges from the viewpoint of hydraulic mechanism and stability characteristics. The results showed that the index mean value under test conditions of slope flow was 0.536, the fluid state was turbulent flow, and the flow pattern was specific jet. Under artificial roughness conditions, with the increase of discharge, the evolution of flow was from instability to roll wave quenching and loss stability. During this period, the surface of water flow was changed greatly. The critical flow rate of roll wave quenching was decreased with the increase of slope, and the quenching critical Reynolds number was varied from 509 to 602 and Froude number was varied from 3.29 to 7.39. The critical Reynolds number for unstable laminar flow was ranged from 778 to 961, and Froude number was ranged from 3.57 to 8.47. With the increase of flow length, the variation of wave celerity was small, but the wavelength and wave amplitude were increased, and the frequency was decreased, polymerization was occurred for roll waves along slope distance. When the unit width discharges and slope were increased, wave celerity and frequency were also increased, but the wavelength was changed little, and wave amplitude was changed in the form of single peak. The research results can provide theoretical basis for studying of soil erosion on the slope, and promote the extension of traditional hydraulics theory to overland flow. 