The interactions between humus particles and metal ions profoundly affect occurrence of some soil micro-and macro-phenomena. As humic acid is the main component of soil humus, process of the aggregation of humic colloidal particles and structure of the resultant aggregates as affected by concentrations of Ca(NO₃)₂ and Cu(NO₃)₂in the solution was studied for comparison analysis in this research project using the light scattering technique. Results show that the difference between Ca(NO₃)₂and Cu(NO₃)₂ in adsorption to the surface of charged colloids greatly affected aggregation of humic colloids. The stability of scattered light intensity reflected stability of the system. Scattered light intensity could remain steady in the Ca(NO₃)₂ system with the electrolyte varying in a wide range from 0 mmol L^-1 to 20 mmol L^-1 in concentration, but in the Cu(NO₃)₂ system, the range was much narrower, from 0 mmol L^-1 to 3 mmol L^-1 only. In the two electrolyte systems, with rising electrolyte concentration, effective diameter of the humic aggregates increased linearly first and then as a power function of time, but the process of humic aggregation is much more sensitive to the variation of Cu(NO₃)₂ concentration than to that of Ca(NO₃)₂ concentration. The mean aggregation rate of humus colloids in the solution of 1 mmol L^-1 Cu²⁺ reached 69.55 nm min^-1, which is nearly 3 times as high as that (23.94 nm min^-1) in the solution of 7.5 mmol L^-1 Ca²⁺. Obviously the mean aggregation rate is much higher under the action of Cu²⁺ than under the action of Ca²⁺. In the Ca(NO₃)₂ system, the higher the electrolyte concentration, the more open, the structure of the resultant aggregates, which became more open or loose in structure and smaller in fractal dimension after being set aside for 50 days, suggesting that the aggregation process is reversible. However, in the Cu(NO₃)₂ system, the aggregates formed under the action of Cu²⁺ were quite open in structure at their initial stage, but they became higher in fractal dimension and more compact in structure after being set aside for 50 days, suggesting that the aggregation process is irreversible. All the findings provide a new way of thinking for understanding the mechanism of the formation of humic supermolecular aggregates.