NOVELTY - Light substrate containing fermented sawdust comprises fermented sawdust, carbonized rice husk and calcium superphosphate. Preparation of the light substrate comprises (i) adding organic compound fertilizer, urea and water to prepare solution; (ii) spreading the solution on sawdust, pressing the sawdust, stacking, and carrying out anaerobic fermentation; (iii) turning the sawdust stack, and spreading the solution to make water content of wood meal to reach 55-60%, stacking, and carrying out anaerobic fermentation; (iv) pressing, stacking, carrying out anaerobic fermentation; and (v) drying.    USE - Used as light substrate containing fermented sawdust.    ADVANTAGE - The light substrate: utilizes wide source of raw materials, which are rich in organic matter; has low cost and good air permeability; increases seedling survival rate of trees up to 95%; provides 90% seedling rate. The method is simple and economical.    DETAILED DESCRIPTION - Light substrate containing fermented sawdust comprises fermented sawdust, carbonized rice husk and calcium superphosphate according to weight ratio of 20-49.5:30-50:0.2-0.8. Preparation of the light substrate comprises (i) adding organic compound fertilizer, urea and water according to ratio of 1:10-30:1000-1500 to prepare solution; (ii) uniformly spreading 2-4 times of solution on sawdust, pressing the sawdust, stacking, inserting a thermometer into the wood chips, and carrying out anaerobic fermentation using sealed film; (iii) when temperature of the anaerobic fermented sawdust stack reaches 58-62 degrees C, carrying out turning the sawdust stack to be loose, and spreading the solution to make water content of wood meal to reach 55-60%, continuously pressing, stacking, and carrying out anaerobic fermentation; (iv) when temperature of the anaerobic fermented sawdust stack reaches 45-50 degrees C, scarifying the sawdust stack, then pressing, stacking, carrying out anaerobic fermentation for 45 days until the fermented sawdust becomes loose, soft and elastic, when it is brown, stopping anaerobic fermentation; and (v) drying the fermented sawdust at 60-80 degrees C until the moisture content of the fermented sawdust is less than 20%. An INDEPENDENT CLAIM is also included for preparing the light substrate containing fermented sawdust, comprising (i) preprocessing the raw materials; (ii) mixing the raw materials, and adjusting humidity to 50-55%; and (iii) filling and sterilizing: preparing the mixed material into the light substrate using a light substrate net bag manufacture machine, filling in a semi-degradable nonwoven fiber material, where the diameter of the net bag container is 3-4.5, soaking the net bag container in 0.5% potassium permanganate solution for 10-12 hours, sterilizing, and then cutting the net bag into 10-15 cm of container section.