Polyadenylation is a key step for 3’end formation of pre-mRNAs and plays an important role in eukaryotic gene expression and regulation. This process is subject to significant regulation by a complex of cleavage and polyadenylation apparatus. CPSF160 is a core component of the cleavage and polyadenylation specificity factor (CPSF) complex. It functions as an essential scaffold and preorganizes other factors in human as shown by biochemical and structural evidence. However, its genetic role is less clear. Using Arabidopsis as a model system, we collected /generated T-DNA insertion mutants and low expression and over expression transgenic lines to study CPSF160’s function in polyadenylation and development. Preliminary results showed that T-DNA insertion in introns and exons of CPSF160 resulted in homozygous lethal. T-DNA insertion in promoter led to over expression of CPSF160 and the mutants showed tolerance to oxidative stress and sensitivity to salt stress. These results suggested that CPSF160 is an essential gene in Arabidopsis and may function in response to environmental stresses. Phenotypic study showed that both low expression and over expression of CPSF160 caused early flowering and abnormal development of inflorescence, along with defects of flower buds and change in leaf color. These results indicated that the expression level of CPSF160 plays a crucial role in Arabidopsis development.