Abstract: To analyze the codon usage pattern of chloroplast genome in Catalpa fargesii, C. fargesii chloroplast genome codons were taken as the research object and 38 protein coding sequences were screened out in this study. CodonW and CUSP online software were used to carry out the neutral plotting, ENC-plot and PR2-plot analyses. The results showed that the average GC content of codons in the chloroplast genome of C. fargesii was 39.03%, and the GC content at different positions was GC₁（47.51%）＞GC₂（40.80%）＞GC₃（28.78%）. The base preference ended in A and U of the chloroplast genome. The effective codon number ENC ranged from 34.93 to 55.78, with an average value of 46.61. There were 25 ENC values greater than 45, indicated that the codon preference was weak. The relative synonymous codon usage（RSCU） analysis showed that there were 30 codons terminated as A or U when RSCU＞1, indicated that their codon preference ends in A/U. The neutral drawing analysis showed that the correlation between GC₁₂ and GC₃ was not significant and the correlation coefficient and regression coefficient of GC₁₂ and GC₃ were-0.023 0 and-0.025 5, respectively, indicated that selection had an important influence on codon usage preference. ENC-plot analysis showed that most of the genes were distributed under the standard curve. There were 13 for ENC frequency ratio in the range of-0.05 to 0.05, indicated that the codon bias was mainly affected by the selection. Most of the genes in the chloroplast genome of C. fargesii were distributed in the lower right of the plan by the PR2-plot analysis, that was, T＞A, G＞C, indicated that there were other factors that affect its codon usage preference in addition to the nucleotide composition. Further correspondence analyses found that the contribution rate of the first axis was 15.21%, the contribution rate of the second axis was 13.20%, the contribution rates of the 3 rd and 4 th axes were 8.82% and 7.35%, respectively, and the cumulative contribution rate of the first 4 axes was 44.58%, the correlation with ENC had reached a significant level. The above analyses results indicated that the codon preference of the chloroplast gene of C. fargesii was affected by selection and mutation factors. In the end, 15 codons such as UUU, UUA, CUU, etc. were determined as the optimal codons in the chloroplast genome of C. fargesii, showed a strong preference for the high representativeness of NNA and NNU codons. This study would provide a reference for future research on C. fargesii chloroplast genetic engineering, genetic diversity analysis, provenance identification, etc. It also provided a theoretical basis for the study of the evolutionary mechanism of Catalpa chloroplast genome.