This study was designed to investigate the formation and effect of inclusion complex of Avermectin-β-cyclodextrin based on the accommodation property of β-cyclodextrins molecular cavity. The inclusion complex of Avermectin-β-cyclodextrin was prepared using saturated solution method and high performance liquid chromatography (HPLC) was employed to determine its entraping efficiency. The formation of Avermectin-β-cyclodextrin inclusion complex was also demonstrated by infrared spectroscopy(IR). The change of chemical structure produced by photocatalysis of Abamectin was analyzed and the effect of inclusion complex to strengthen the photolysis stability of Abamectins chemical structure was studied. The results show that the entraping efficiency of the inclusion complex was 40.5%. The IR analysis presents that the intermolecular hydrogen bond was formed in the Avermectin-β-cyclodextrin inclusion complex, indicating the composition effect was different from physical mixture. The lactones structure of Avermectin B1a can be photodecomposed and disrupted. After decomposition, the infrared stretching vibration peak of C—O—C structure disappeared and the lactone bond was significantly broken. The lactones structure of avermectin B1a was covered by the inclusion molecular loci in β-cyclodextrin after the formation of avermectin-β-cyclodextrin inclusion complex, providing a good photophobic protection for C—O—C structure in the macrocyclic lactone structure of avermectin B1a and improving the photostability of avermectin B1a molecule. The innovation of this study is that the structure and the characters of the prepared avermectin-β-cyclodextrin inclusion complex were analyzed using spectrum methods. This inclusion complex is expected to be the ideal intermediate in the construction of protective controlled release formulation of avermectin.