Abstract:Suppression subtractive hybridization (SSH) based on magnetic beads technology was used to screen day-night differential expression genes of Paraquilegia microphylla living on the scree of the Baima snow mountain of Tibetan plateau. The daytime sample was used as tester and nighttime sample as driver for further analysis. Finally, 96 differential ESTs between two samples were sequenced. Sequences were analyzed with BlastX, Blast2go and KEGG. The results indicated that most differential expression proteins are related to material and energy metabolism, biosynthetic process, have nucleic acid binding, protein binding and transferase activity; and a few are responsive to stress, etc. These results will provide some prerequisites for further researches on alpine plants under harsh environments.