The ubiquitin proteasome system (UPS) has a significant impact on the procedures such as mitosis, cell signal transduction and its procedural death. The downstream signal path is regulated by degrading the target protein through it. To regulate the target protein rapidly and accurately, the UPS mainly depends on two enzymes families, the ubiquitination enzymes (UBs) and deubiquitination enzymes (DUBs). Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) is one of the critical enzymes among all that in DUBs family. It belongs to the cysteine hydrolase which is composed of 223 amino acids. It is reported that UCH-L1 identifies and cracks the 76th glycine on the carboxyl-terminal, which cuts off the ubiquitin from the poly-ubiquitination chain of the target protein, to prevent it from being degraded by the UPS. The degradation speed of the target protein is negatively regulated by DUBs in this way and the free monoubiquitin is generated through it to be submitted to the next target protein for its ubiquitination. In recent study, it is reported that UCH-L1 is a multi-functional molecule. Firstly, we explain the molecule structure of UCH-L1 and its basic biological functions, including the deubiquitination and stabilizing the monoubiquitin. Besides, it owns the ability of ubiquitin ligase and takes part in the formation procedures of microtubule, synapses and the bacteria invasion.