Casparian strips are a cellular feature found in the roots of all higher plants, which are ringlike, hydrophobic cell wall impregnations that tightly attach with the endodermal cell membrane. Casparian strip acts as a barrier to the free diffusion of solutes from the soil, and forces ions through endodermal cell into the stele. Casparian strip was found in 1865, but many botany textbooks cannot give completely correct information on it. The mechanism of its formation was gradually aware until Casparian strip membrane domain proteins (CASPs) were characterized and the substance of Casparian strip were revealed. The scaffold, which consists of CASPs and receptorlike kinases, was needed for Casparian strip formation. Casparian strip diffusion barrier in Arabidopsis is made of a lignin, and NADPH oxidaseRBOHF, PeroxidasePer64 and ESB1 dirigent protein were used to catalyze the polymerization with monolignol, which was transported from cell into Casparian strip membrane domain by ABCG transporter. Here, we reviewed the major findings and models related to Casparian strip and its function in light of recent molecular data. This article can provide a framework and inspiration for further molecular dissection.