Abstract: Chitin widely existed in world and rich in resource, and it is the second largest high molecular compound after cellulose. Chitosan with biocompatibility, bio-functional groups, and safety and non-toxic was reviewed. The paper was gaining more attention in the agriculture. It could be used as soil improvement agent, plant disease inhibitors, seed-coating agent, feed additive, plant growth regulators, cold-resistance agent as well as pesticide carrier and had already been verified in crops, fruits and animal husbandry and aquaculture. The mechanism of action of chitin and chitosan in the various roles of agriculture was researched as well as the main research achievements of predecessors, especially the treatment of chitin and chitosan as seed coating, to coat the seeds or seed soaking effects on crop growth and development as well as its main application mechanism. It concluded that seed-coating or soaking treatment of different crops by chitosan could influence the growth of crops, and analysis showed that chitin and chitosan’s treatment played a very important role on seeds germination and seeding growth, and it could be widely used in the production of crops, and it also had a remarkable economic benefit and research value.