Mucin is the key factor to determine the stability of tear film and is crucial to maintain ocular surface homeostasis. Goblet cells can alter the secretion of mucin in corneal and conjunctival epithelial cells, contributing to dry eye disease and ocular surface inflammation. Based on the understanding of mucin biology, this review makes a summary on the potential relationship between mucin dysfunction and ocular surface diseases, and we hope to deepen the understanding of the importance of mucin and select the most appropriate treatment plan on the basis of ocular surface diseases.