Anabaena sp. PCC 7120 is an important model strain in the field of cyanobacteria research.Controlling the expression level of gene is one of the most important ways to investigate gene functions.There are a variety of matured gene induction systems available in cyanobacteria. However,no controllable protein degradation system is available in cyanobacteria yet. This work is based on the protein quality control system in Mesoplasma florum and aims to construct an inducible protein degradation system facilitating the investigation of essential genes in Anabaena PCC 7120. Results showed that the degradation or decrease of the target proteins was not detected.It is indicated that the constructed system needs to be further improved.