An in-situ chemical oxidation high pressure injection optimization remediation method for soil and groundwater. A field test determines the diffusion radius of the injection agent in a typical formation, the maximum single-hole grouting amount per linear meter and the injectability parameter. Density-increased supplementary investigation, soil and groundwater data analysis, is divided by spatial distribution into four concentration main partitions, eight concentration sub-partitions. By optimizing the single-hole grouting amount per linear meter, the preparation concentration of the oxidant, and the parameters of the formulation of each partition, the optimization of the dosing ratio of remediation agent of each partition is achieved. The specific construction performance is to adjust the lifting speed of the high pressure injection drill pipe during the injection process for finally achieve the purpose of reducing the dosing ratio parameters of the agent in the remediation plot.