Heterogeneous Fenton technology is effective in degrading residual pesticides in soil, but the reduction of Fe(III) in the mineral structure presents a bottleneck. This study combined rice straw with Schwertmannite (Sch), ferrihydrite (Fh), and magnetite (Mag) via a hydrothermal process to obtain iron oxides-hydrothermal carbon composites (Sch@HTC, Fh@HTC, and Mag@HTC). Poor-crystallized Sch and Fh, which were more capable of accepting electrons compared to well-crystallized Mag, exhibited obvious phase transformation to highly active Fe(II)-mineral (humboldtine) via the combination of oxalic acid, an intermediate product, with reduced Fe(II), while Mag was hard to achieve. After hydrothermal treatment, all composites showed enhanced catalytic activity, which increased with the degree of phase transformation. Especially, Sch@HTC demonstrated the highest catalytic activity, degrading 85 % of metolachlor in soil within 24 hours, 2-10 times faster than the others. Surprisingly, the solid-phase Fe(II) in soil increased slightly after the Fenton reaction. Moreover, the in-situ fluorescence intensity of HO