The invention discloses a permanganate gel slow release agent and a preparation method thereof .Colloid silicon dioxide is adopted as a coating substance, a potassium permanganate oxidizing agent is used as a core material, and potassium permanganate gel with a slow release effect is prepared according to the sol-gel principle of silicon dioxide .According to the preparation method, a potassium permanganate solution is added into a silicon dioxide gel solution, and potassium permanganate solution gel is prepared into the gel slow release agent with silicon dioxide gel as the outer wall and potassium permanganate as the inner core by controlling the sol-gel process of silicon dioxide .By means of the prepared potassium permanganate gel, the release rate of potassium permanganate can be effectively controlled, non-selective consumption of the potassium permanganate oxidizing agent is reduced, the utilization rate of the potassium permanganate oxidizing agent is increased, and the purpose of removing chlorinated organic pollutants continuously and efficiently by means of in-situ chemical oxidation is achieved.