Protein is one of the most important biological macromolecules. In the protein translocation system, many proteins, after being synthesized in the ribosome, will enter their corresponding subcellular organelles through the endoplasmic reticulum or plasma membrane to play a important role in biological functions. There are three pathways for protein secretion, which are Sec pathway, Tat pathway and SRP pathway. In this paper, we present a basic transport pathway of protein, and mainly introduce the transloca...