The mechanism of B-type monoamine oxidase inhibitors for Parkinson’s disease can be divided into two aspects: one is neuroprotective and the other is symptomatic therapeutic. Type B monoamine oxidase (MAOB) is a mitochondrial membrane complex enzyme that plays an important role in the dopamine metabolic pathway. It breaks down dopamine into homovanillic acid, accompanied by the generation of the free radical H2O2, which has a toxic effect on nerve cells; it also activates 1-methyl-4-phenyl 1,2,3,6-tetrahydropyrimidine (MPTP), a chemical that induces Parkinson’s disease. It can be speculated that inhibiting the activity of MAOB can block the degradation of dopamine and reduce the generation of oxygen radicals. It can also block the conversion of MPTP to MPP+ and inhibit the production of peroxides during the oxidative metabolism of dopamine, thus delaying the process of nigrostriatal cell death and altering the course of PD. At the same time, due to the inhibition of dopamine degradation, the concentration of dopamine in the brain is increased, which has the effect of improving the symptoms of Parkinson’s disease. The representative drugs of MAOB are Slegiline (Kingspine and Midopir). Its side effects are more common with dizziness, sleep disturbance, nausea, and postural hypotension in individual patients after treatment. However, most of the symptoms are mild and do not affect the continuation of medication. The new generation MAOB drug is resagiline, which has not yet been marketed in China.