Abstract: Abstract: To study the molecular mechanism of Larix somatic embryogenesis, a differentially expressed cDNA library of Larix somatic embryo in the period of maturation was constructed using suppression subtractive hybridization (SSH). The cDNA from the cultures at the stage of somatic embryo maturation of embryogenic cell line Y35 of L. leptolepis ×L. princi-pis-rupprechtii was used as the tester and the cDNA from its subcultured callus was used as the driver. Eight hundreds ran-domly selected positive clones were sequenced, and 468 UniGenes were obtained finally. According to their function, these ESTs were classified into 19 categories and were involved in many biological process related to plant growth and develop-ment such as metabolism, transcription, signal transduction, transport facilitation, cell growth and division, cell structure, cell fate, protein synthesis or degradation, defense etc. Real-time PCR results of several ESTs showed that they were all differentially expressed at the different stages during cell line Y35 somatic embryo maturation.