Actinic keratosis (AK) is a precursor to cutaneous squamous cell carcinoma (SCC),and molecular mechanisms of transformation from AK to SCC have been a research hotspot.This review focuses on four aspects of the molecular mechanisms,including chromosomal variation,gene mutations,signaling pathways and other factors,summarizes advances in selective mutations in chromosomes 3p,9p,9q,13q,17p and 17q,heterozygous deletion mutations in chromosome 18q,mutations of p53,p16 and Ras genes,abnormality of the transforming growth factor β1 signaling pathway and Fas/FasL signaling pathway,and aberrant expression of matrix metalloproteinases in the transformation from AK to SCC,which will provide a reference for further researches.