A monocyclic β-lactam-siderophore conjugate represened by formula (I), an optical isomer thereof or a pharmaceutically acceptable salt thereof: wherein X = CY or N, Y is H or a halogen; R is a carboxyl group, -COOR 1 or -CONR 2 R 3 ; an unsubstituted C 1-6 linear alkyl group, an unsubstituted C 3-6 branched alkyl group, a C 3-6 cycloalkyl group or an unsubstituted C 2-7 alkenyl group; a substituted C 1-4 linear alkyl group or C 3-6 branched alkyl group, wherein the substituent is a hydroxyl group, an amino group, a cyano group, -OR 1 , -SR 1 , -S(O 2 )R 1 , -NR 2 R 3 , and a halogen; a substituted or unsubstituted phenyl group, wherein the substituent in the substituted phenyl group is 1 to 3 substituents independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 and a halogen; or a substituted or unsubstituted 5- or 6-membered heteroaryl ring group having 1 to 4 hetero atoms independently selected from the group consisting of N, S and O, wherein the substituent in the 5- or 6-membered heteroaryl ring group is independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 , and a halogen; R 1 is a C 1-6 linear alkyl group, a C 3-6 branched alkyl group or a C 3-6 cycloalkyl group; R 2 and R 3 are each independently a hydrogen, a C 1-6 linear alkyl group, a C 3-6 branched alkyl group or a C 3-6 cycloalkyl group; the halogen is F, Cl, Br or I; preferably F, Cl or Br; a stereo configuration of an alpha carbon may be of S type or R type or (R, S) type. R is a carboxyl group, -COOR 1 or -CONR 2 R 3 ; an unsubstituted C 1-6 linear alkyl group, an unsubstituted C 3-6 branched alkyl group, a C 3-6 cycloalkyl group or an unsubstituted C 2-7 alkenyl group; a substituted C 1-4 linear alkyl group or C 3-6 branched alkyl group, wherein the substituent is a hydroxyl group, an amino group, a cyano group, -OR 1 , -SR 1 , -S(O 2 )R 1 , -NR 2 R 3 , and a halogen; a substituted or unsubstituted phenyl group, wherein the substituent in the substituted phenyl group is 1 to 3 substituents independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 and a halogen; or a substituted or unsubstituted 5- or 6-membered heteroaryl ring group having 1 to 4 hetero atoms independently selected from the group consisting of N, S and O, wherein the substituent in the 5- or 6-membered heteroaryl ring group is independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 , and a halogen; a carboxyl group, -COOR 1 or -CONR 2 R 3 ; an unsubstituted C 1-6 linear alkyl group, an unsubstituted C 3-6 branched alkyl group, a C 3-6 cycloalkyl group or an unsubstituted C 2-7 alkenyl group; a substituted C 1-4 linear alkyl group or C 3-6 branched alkyl group, wherein the substituent is a hydroxyl group, an amino group, a cyano group, -OR 1 , -SR 1 , -S(O 2 )R 1 , -NR 2 R 3 , and a halogen; a substituted or unsubstituted phenyl group, wherein the substituent in the substituted phenyl group is 1 to 3 substituents independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 and a halogen; or a substituted or unsubstituted 5- or 6-membered heteroaryl ring group having 1 to 4 hetero atoms independently selected from the group consisting of N, S and O, wherein the substituent in the 5- or 6-membered heteroaryl ring group is independently selected from the group consisting of a hydroxyl group, a cyano group, -R 1 , -OR 1 , -NR 2 R 3 , and a halogen; R 1 is a C 1-6 linear alkyl group, a C 3-6 branched alkyl group or a C 3-6 cycloalkyl group; R 2 and R 3 are each independently a hydrogen, a C 1-6 linear alkyl group, a C 3-6 branched alkyl group or a C 3-6 cycloalkyl group; the halogen is F, Cl, Br or I; preferably F, Cl or Br; a stereo configuration of an alpha carbon may be of S type or R type or (R, S) type. <EOS>