Clean fracturing fluid

The invention provides a clean fracturing fluid, which comprises the following ingredients (by weight): 2-4% of a densifier, 0-8% of potassium chloride, 0-10% of a modifier, 2-5% of a temperature-resistant reinforcing agent and the rest of fluid preparation water. The fracturing fluid can adopt acidic or alkaline fresh water or highly saline acid fracturing backflow fluid. After mechanical impurity removal treatment, highly saline backflow fluid can be used in fracturing fluid preparation of the next well without adjusting fluid preparation water quality in advance. Then, water quality chemical treatment process is omitted, and operating cost is greatly reduced. During site operation, efficient sand-carrying of the fracturing fluid is realized through a continuous mixing mode. Therefore, acid fracturing modification of a reservoir stratum and no falling of spent liquor during the whole oil and gas testing process are achieved, and ''zero pollution'' of borehole operation site is realized. The invention is helpful for cleaning and efficient production.