Triblock Copolymers are copolymers in which the basic unit consists of three block chains. The three polymers can be completely different, or can be repetitions. Therefore, in terms of polymer structure, triblock copolymers can be divided into symmetric copolymers and asymmetric copolymers. Symmetric triblock copolymer formation consists of two types of polymers (A, hydrophobic polymer and B, hydrophilic polymer), such as ABA and BAB triblock copolymers. Asymmetric triblock copolymers (ABC triblock copolymers) consist of three different types of polymers. Depending on the application, both of them can be composed of hydrophilic or hydrophobic polymers. Therefore, different types of nanostructures, such as star-like micelles, flower-like micelles, and polymeric vesicles, can be prepared from these block copolymers. This would have great potential to deliver various types of drugs, such as chemical drugs, genes and contrast agents.