As a result of the rapid development of industry, the heavy metal contamination of landfill leachate has become more serious. Adsorption is an effective method that can remove heavy metal ions from landfill leachate. Na-bentonite was selected as the adsorbent for the adsorption of heavy metal ions (lead, cadmium, copper) from landfill leachate in both single and competitive systems. Batch experiments were conducted to study the effects of contact time, pH value, temperature, and initial concentration on adsorption efficiency. Adsorption behavior was investigated by means of adsorption isotherms, adsorption kinetics, and adsorption thermodynamics. The study results show that: 1. The amount of heavy metal ions adsorbed by Na-bentonite increases with increasing contact time, pH value, temperature, and initial concentration of heavy metal ions. 2. Adsorption behavior is suitable for modeling with the Langmuir isotherm and a pseudo second-order kinetic model. 3. The adsorption of lead and cadmium are thermodynamically spontaneous, the adsorption of copper is not spontaneous, and the adsorption processes of lead, cadmium and copper are all endothermic using thermodynamic analysis. 4. Competitive adsorption between lead, cadmium, and copper occurs in competitive systems.