Abstract: To understand the effect of alkali and alkaline earth metals on the gasification reactivity of biomass char under pressurized conditions, the biomass char prepared by pyrolysis at 800 ℃ was used as the research object. The pyrolyzed biomass was pre-treated with deionized water and dilute hydrochloric acid solution, respectively. Gasification study was conducted on the raw biomass char and the two pre-treated samples in a wire-mesh pressurized reactor under various gasification agents, temperatures, and pressures. Results show that most of the potassium and some of the calcium and magnesium can be removed from the water-washed samples, while no alkali and alkaline earth metals are detected in the acid-washed biomass char sample. At 850 ℃, the gasification reactivity is not affected by pressure, whereas at 1 000 ℃, pressure has a promotional effect on gasification reactivity. Water-soluble potassium and calcium significantly enhance the gasification reactivity with both CO₂ and steam, and their catalytic effects are enhanced at high temperatures. The water-insoluble calcium only slightly increases the gasification reactivity. At 850 ℃, the reaction orders with respect to CO₂ partial pressure are close to 0 for all samples, while at 1 000 ℃, the reaction order is greater than 0.