The invention discloses an alcamines compound acid gas purifying agent used for desorbing acid pollutants in gas. The purifying agent is prepared from, by weight, (A) 30-45 parts of one or more kinds of amine shown in the formula 1, wherein R1 and R2 independently represent C1-C4 alkyl groups, R3, R4, R5 and R6 are independently selected from hydrogen and C1-C4 alkyl groups, R7 and R8 are C1-C4 alkyl groups independently, x and y are integers ranging from two to four, and z is an integer ranging from one to three; (B) 10-20 parts of polyethylene glycol dimetyl ether (NHD); (C) 35-60 parts of one or more kinds of alcamines shown in the formula 2, wherein R2 is the same as the R2 in the formula 1, R is independently selected from hydrogen and C1-C4 alkyl groups, and n is an integer ranging from one to four. Compared with various compound absorbents, the purifying agent has the advantages of being higher in absorbing effect, small in solvent consumption and high in regeneration rate.