The invention discloses a negative ion biomass aldehyde removing agent. Through combination of natural herbal plants and combination of biomass raw materials and negative ions, the negative ion biomass aldehyde removing agent utilizes raw materials having a wide source and low prices and contains a variety of active groups. An amino group and formaldehyde undergo a nucleophilic addition reaction, hydroxyl and formaldehyde undergo an electrophilic addition reaction and an aldehyde substance and formaldehyde undergo an aldol condensation reaction. The formaldehyde reactions are irreversible chemical reactions so that the elimination of formaldehyde is realized, a formaldehyde removal rate is 95% and a sterilizing rate is 95%. The biomass produces glucose and fructose under action of glycohydrolase and the glucose and fructose undergo an aldol condensation reaction with formaldehyde so that formaldehyde is further eliminated. The negative ion biomass aldehyde removing agent is toxic to the human body, does not produce the environmental pollution, acts fast, has durability, has effects of elimination of formaldehyde, air purification, sterilization, disinfection and mosquito repellent, can relieve fatigue, restore consciousness, improve spirit and increase negative ion content of indoor air, is conducive to human health, is produced by simple processes and realizes a low production cost.