LAS/LS subfamily plays an important role in the regulation of plant branching and development. The 35s∷SpsLAS overexpression vector was constructed and transformed into wild type A.thaliana. These transgenic A.thaliana were screened by phenotype. The expressions of genes related to branching, auxin and cytokinin were analyzed by fluorescence quantitative PCR. The results showed that: (1) 35S∷SpsLAS overexpression vector was successfully transformed and nine homozygous transgenic lines of A.thaliana were obtained. The germination speed of transgenic lines were faster and life cycle was longer than that of wild type. Seven transgenic lines of them showed rapid growth, increased plant height, enlarged rosette leaves and more branches. Two lines showed a series of changes as dwarfing, more branches and lower fertility. (2) Fluorescent quantitative PCR showed that there were no significant changes for auxin and cytokinin pathway related genes at 24 h of seedling, while upregulated at 4 d. Gene expressions of RAX1 and RAX3 related branching were upregulated while MAX1, MAX3, REV and AXR1 had no obvious changes at 30 d. The research showed that the overexpression of SpsLAS gene has significant effects on plant architecture and rosette leaves of A.thaliana and laid the foundation for further research on the regulation of branching mechanism.