A novel, environmentally friendly seed coating agent for maize which is mainly made up of natural polysaccharide polymer extracted from pollution-free aquatic in the deep sea, and supplemented by other additives. Laboratory and field’s test results showed that the antibacterial rate of this seed coating agent came up to more than 90%, the antifeeding rate of insect pests came up to more than 81%, maize yield was increased by 14.4% and 17.3% than that of conventional seed coating agent and blank control treatment respectively, and the LD50 of this seed costing agent is 10 times more than conventional seed coating. It is more environmentally friendly and safer than the conventional seed coating agent, and it has five major characteristics including antibiosis, insect repellent, enhance tolerance to stress, increasing yield, safety and environmental friendship. Through researching and testing the activity of several specific enzymes (such as POD, CAT, SOD, etc.) and the proportion of chlorophyll in the seedlings of maize, it had been found that the increase of resistance and yield of maize can be mainly chalked up to activating the activity of several kinds of enzyme (such as POD, CAT, SOD, etc.) and increasing the portion of chlorophyll in maize by this seed coating agent.