Trajectories of directional jets and characteristics of annular helical flow in horizontal wellbore cleanout were investigated by the computational fluid dynamics method. For an annular helical flow, the drive source is the partial lateral jets, while the forward and backward jets provide the fluid source. The axial and radial distributions of annular and tangential velocity were analyzed comprehensively. As the distance increases and the flow rate decreases, the strength of the helical flow weakens dramatically. As the rotating speed of the jetter increases, the helical strength enhances slightly. The best performance to achieve annular helical flow is water, followed by Guar-B and Guar-A. This article is beneficial to study the solid transportation in helical flow and optimize the operation parameters.