Shading (i.e. shading) is the latest model of the covering material special agriculture, fishery and animal husbandry etc. at present, using polyethylene as raw material, ultraviolet stabilizer and anti oxidation treatment, with strong stretching resistance, anti-aging, corrosion resistance, radiation resistance, light, etc.. Mainly used for cooling, vegetables, flowers, incense, Gu mushroom, seedlings, herbs, ginseng, Ganoderma lucidum. Net is nearly 10 years to promote a protective cover material, covering after a summer light rain, moisture, cooling effect. In winter and spring, there is a certain heat preservation and humidifying effect after the cover of winter and spring. General winter planting leafy vegetables in the shade net directly cover surface (surface coverage), in case of low temperature damage, because of its light weight, only 45 grams per square metre, the tree has grown into a high leaf will not overpower, bending, reduce commodity. It also has a certain air permeability, the leaf surface is still dry after covering, reducing the occurrence of disease. It also has a certain light transmittance, and will not cover "cover the yellow" after covering. A winter celery, inside of the surface coverage for cold protection, the results showed that the surface coverage in the shade outside -6 deg.c, celery leaves not found a lot of ice; and the single shed controls, especially in the upper leaves was frozen hard, by testing coverage than the control of high temperature of 1.5 DEG C.