Abstract: Trans-translation is a mechanism that fixes stalled translation course. tmRNA is the core of trans-translation and it has dual function as a tRNA and a mRNA. tmRNA recognizes the ribosome carrying truncated mRNA with specificity under the help SmpB protein. It can be directed to A site by ribosomal protein S1. At first tmRNA prolongs the genetic message on the stalled mRNA, then stop codon terminates peptide synthesis to form a nascent chain with the tag sequence. Finally tmRNA-SmpB system frees stalled ribosomes and directs degradation of the products of these frustrated protein synthesis reactions. This paper introduces the most recent studies on trans-translation.