Theoretical calculations have been performed for the complexes of formamide(FA)with methanol and its derivates(MAX,X=F,Cl,Br,NO2,H,OH,CH3,and NH2)to study their structures and properties.Substituent effects on the hydrogen bond(H-bond)strength and cooperative effect by using water and its derivatives(HOZ,Z=H,NH2,and Br)as weak interaction probe were also explored.The calculation results show that electron-donating groups strengthen the weak interaction between formamide with methanol whereas electron-withdrawing groups weaken it.The cooperativity is present for the N-H…O H-bond in MAX-FA-HOZ and the cooperative effect increases with the order of HONH2,HOH,and HOBr.In addition,we investigated the interaction between FA with hypohalous acids(HOY,Y=F,Cl,and Br).It was found that the weak interaction between FA and HOY became stronger with the increase of the size of halogen atom.The nature of the halogen atom has negligible impact on the strength of the H-bond in MAX-FA(X=F,Cl,and Br),whereas it has an obvious influence on the strength of the H-bond in HOY-FA(Y=F,Cl,and Br).