Penicillin binding proteins (PBPs) are a class of membrane proteins that are widely present on the surface of bacteria. They are the main target of β-lactam antibiotics. In the process of the bacterial cell wall peptidoglycan synthesis, PBPs play key roles of glycosyl transferase, peptidyl transferase and D-alanyl-D-alanine carboxypeptidase and thus are indispensable for bacterial growth. Different bacteria contain various PBPs. Changes of protein structure, increase of quantity, decrease of susceptibility to antibiotics and production of new PBPs are important reasons resulting in drug-resistance to β-lactam antibiotics. With wide use of different antibacterial agents, the problem of bacterial resistance is becoming increasingly serious. Therefore, research on PBPs has been carried out in recent years around the world. In this paper, the classification, structure and function of PBPs, their relationship with bacterial drug-resistance and detection methods are summarized. This paper also indicates future research directions.