Abstract: In order to develop new sustained,friendly environmental and controlled release formulation,an inclusion compound of allethrin with hydroxypropyl-β-cyclodextrin (HP-β-CD) was studied.HP-β-CD solubilizing allethrin was studied by the way of the phase solubility diagram.Allethrin's inclusion complex with HP-β-CD was prepared using the method of coevaporation,and the inclusion complex in solid state was evaluated by differential scanning calorimetry(DSC),Fourier-transform IR,thermal gravimetric analysis(TG) and NMR.The results showed that its solubility was significantly increased by the complexation of allethrin and HP-β-CD;The phase solubility diagram with HP-β-CD was classfied as AL-type,indicating the formation of 1:1 stoichiometric inclusion complex;The formation of the inclusion complex was demonstrated by the study of DSC,TG,IR and NMR.The configuration of allethrin/HP-β-CD complex showed that the pentagon ring of allethrin entered the cavity of HP-β-CD,and the barycenter of the pentagon ring located around the H-5 of HP-β-CD cavity.