The invention relates to a construction process of a long-auger jet-grouting mixing curtain pile. The curtain pile is formed by adopting the steps of pile position determination between two adjacent slope protection piles, lead hole drilling, jet-grouting mixing drilling and jet-grouting mixing drill-hoisting, wherein a long-auger jet-grouting mixing pile drill is adopted in the jet-grouting mixing drilling and the jet-grouting mixing drill-hoisting. The construction process comprises the following steps of: (1) high-pressure rinsing: firstly carrying out jet-grouting mixing drilling from the top to the bottom to reach the designed hole bottom, then carrying out directional jet-grouting hoisting on the drill to reach a hole mouth, and finally carrying out directional jet grouting to reach the hole bottom; and (2) high-pressure cement slurry: firstly carrying out jet-grouting mixing hoisting on the drill to reach the hole mouth, then carrying out directional jet grouting downwards to reach the hole bottom, and finally hoisting the drill to carry out directional jet grouting to reach the designed level to form the pile. The invention has the beneficial effects that: undisturbed soil which remains between a new hole and a constructed slope protection pile after hole leading can be rinsed out by adopting a three-water and three-slurry process so that the cement slurry and the slope protection pile are closely combined without gaps, thereby improving the strength and the water-stop effect of a water-stop curtain; and the hoisting speed of the drill is controlled by a frequency converter, therefore, the production efficiency is improved, and the energy resources are saved.