An anesthesia machine, an anesthetic output concentration monitoring method, system, and device, and a storage medium. The method includes: respectively monitoring a flow of a fresh gas flowing into a breathing circuit and a flow of an inhaled gas of an anesthetized object (S11)； when the inhaled gas flow is greater than a fresh gas flow, respectively monitoring a concentration of anesthetic in the inhaled gas and an exhaled gas of the anesthetized object (S12)； using the exhaled gas anesthetic concentration and a concentration of carbon dioxide in the exhaled gas to calculate a concentration of anesthetic in a gas, reflowing into an inspiratory branch, in the exhaled gas, thereby obtaining a re-inhaled gas anesthetic concentration； and using the fresh gas flow, the inhaled gas flow, the inhaled gas anesthetic concentration, and the re-inhaled gas anesthetic concentration to calculate a concentration of output anesthetic of an anesthetic output device, thereby obtaining an anesthetic output concentration.
