Research about cement treated soil has examined various characteristics of strengthened and stabilized soil, but has mainly focused on either the unconfined compressive strength or potentially toxic element (PTE) stabilizing results respectively in response to cement dosing. This study investigates how factors including cement concentration, lead concentration, humic/fulvic acid content and curing age affect these two geotechnical and environmental characteristics. A laboratory study was conducted to measure unconfined compressive strength, and lead leaching under several test conditions. Knowing that humic acid and fulvic acid can weaken cementation in cement treated soil but can stabilize PTEs such as lead by different chemical reactions, it was found that the acids generally reduce lead stabilization in cement treated soil. In addition, the stabilized strength reaches a peak at a specific lead content in soil. Finally, scanning electron microscopy was used to observe more detailed changes and mechanisms.