Humic acid (HA) and starch (St) were used as raw materials, N,N'-Methylenebisacrylamide (MBAA) as cross-linking agent, Potassium persulfate/Sodium Hydrogen Sulfite (K2S2O8/NaHSO3) as the composite ini-tiator, and the humic acid/starch composite microspheres (CSM) were synthesized by inverse emulsion polymerization. Combining with response surface methodology, the effects of HA/St material ratio, K2S2O8/NaHSO3 dosage, MBAA dosage, composite emulsifier dosage and temperature on the adsorption properties of CSM were discussed. The results showed that the optimum technological conditions were as follows: m(HA): m(St)=1.51:1, K2S2O8/NaHSO3 dosage 0.6 g/0.6 g, MBAA dosage 0.6 g, composite emul-sifier dosage 1.2 g, temperature 50℃, oil-water volume ratio 3:1 and reaction time 3 h. Under these condi-tions, the removal rate of CSM for Cr(VI) (10 mg/L) reached 99.91%. The structure and morphology of CSM were characterized by FTIR and SEM. It was found that HA and St reacted successfully, CSM has regular shape and the surface was rough. The particle size distribution, crystallinity and thermal decompo-sition performance of CSM were measured by laser particle size analyzer, XRD and TGA. The results showed that the particle size distribution of CSM was uniform and the average volume diameter was 19.49μm, the crystallinity of CSM (compared with St) was reduced, and the thermal stability of CSM was good.