Abstract: In order to optimize the operating parameters of an independently developed horizontal ball mill, and to provide basic data for the improvement, scale-up, and application of the equipment, we conducted a quicklime based mechanochemical destruction (MCD) study using HCHs heavily contaminated soil from an organochlorine pesticide factory. Indicated by the removal rate of HCHs over time, charge ratio and material ratio, the two important parameters controlling the performance of MCD treatment were optimized in an orthogonal experiment design. The results showed: ① Charge ratio of 10:1 and material ratio of 1:2 were the optimal operating parameters. Meanwhile, as there was no significant difference between the material ratio of 1:5 and 1:2, the charge ratio of 10:1 and material ratio of 1:5 were selected as the optimal operating parameters for the sake of cost and other practical considerations. Under conditions of charge ratio of 10:1 and material ratio of 1:5, the average HCHs removal rate reached 91.1% at 0.5 h and 96.04% at 1 h, indicating that the optimized parameters were viable. ② HCHs removal rates reached 65.21%~99.94% and 72.44%~99.98% at 0.5 h and 1 h, respectively. It confirms that the horizontal ball mill is able to treat HCHs in contaminated soil efficiently. The horizontal ball mill presented in this study has great potential for scaling up and application in MCD treatment of HCHs contaminated soil. The optimized process parameters may be applied in practice.