Leaves are important vegetative organs in plants， and the leaf margin serration （lobe） has many advantages in production practice. Disclosing the regulation of leaf margin serration has important guiding significance for plant breeding. This article reviews the regulation mechanism of leaf margin serration formation. Several factors such as plant hormones， gene expression， and miRNAs， are involved with roles in shaping leaf margins. Auxin unbalanced accumulation at the leaf margin can promote serration. Auxin-dependent cytokinins （CK） accumulation at leaf margin might result in the leaf shape complexity， while gibberellin （GA） negatively regulates leaf shape complexity. This review further summarizes three main pathways of plant hormones and genes involved in leaf margin serration formation： TCP-CUC-PIN1-Auxin， KNOX-GA/CK， LMI1-CK. The miR164， miR319， polycomb group （PcG） epigenetic modification and alpha-1，2-glucosyltransferase are known to be involved in leaf margin serration formation. The ambient temperature and light intensity regulate the leaf margin development through the KNOX-GA pathway. For instance， high temperature and low light intensity might decrease the complexity of leaf shape. The different genetic mechanisms on the regulation of leaf margin serration in plants are revealed. The genes that modulate or associate with the leaf margin serration are often reported in cash crops. In addition to fruit quality and resistance， ornamental character is one task with significant interest in future breeding of fruit trees.