Removal of heavy metals from wastewater by biosorption is an attractive approach. In this work, the interactions between lead and Typha angustifolia biomass, a cost-effective biosorbent, were investigated. It was found that the interactions between lead and T. angustifolia biomass were complex, and the solution pH was a key factor governing such interactions. The FTIR characterization and the results of blocking experiment indicate the amino, hydroxyl, and carboxyl are the main functional groups contributing to these interactions. A synergistic mechanism involving ion exchange, complexation, and hydrogen binding was elucidated. According to this mechanism, the dominant interactions between the biomass and lead altered with the variation of pH, which was consistent with the experimental results. Additionally, a simple method was explored to estimate the contributions of different interactions between the biomass and lead.