Autophagy is a cellular process for degradation of damaged proteins and organelles via forming autophagosome. Microtubule-associated protein 1 light chain 3 B (LC3B) is a marker protein for autophagy detection. However, in many lower animals, autophagy detection is limited for a lack of available specific LC3B antibody. In the present study, the coding sequence of LC3B of Mytilus galloprovincialis was cloned and inserted into a pET-32a prokaryotic expression vector. To obtain a high-level and soluble expression of recombinant MgLC3B-His protein, the IPTG concentration and induction time were investigated. Then, the purification conditions of this recombinant protein were also studied. Our results showed that MgLC3B was inserted in the pET-32a prokaryotic expression vector successfully. The recombinant MgLC3B-His protein was induced at 20℃, 150 r/min with IPTG concentration of 0.6 mmol/L after 10 h culture. A single-band recombinant protein was obtained after affinity purification. After immune injection, and the rabbit polyclonal antibody was also obtained, with a titer of 25 600. Therefore, our results will be helpful for the investigation of autophagy in mussels and similar species.