The frequency of codon usage often affects the expression of foreign gene in transgenic research. A statistics of the frequency of codon usage in Arabidopsis thaliana was made, and a direct comparison of genctic code preference among Arabidopsis thaliana, Homo sapiens and Escherichia coli was carried out.The results show that Arabidopsis thaliana like Homo sapiens its frequency of codon usage is obviously different from Escherichia coli, and there is a considerable difference between Arabidopsis thaliana and Homo sapiens. The data will give some suggestions to those researchers who want to introduce a animal gene into plant or a plant gene into bacteria.