Codon bias refers to the nonrandom usage of synonymous codons for encoding amino acids in organisms. As it is related to the carrier molecular of genetic information (DNA) and functional molecular (protein) of life, this phenomenon implicates important biological sense. In this review, we summarize the basic theories and analysis methods about codon bias; and present the softwares and websites which are usually used for codon usage analysis. The related fields about codon bias and the research progress are also introduced.