NOVELTY - A Trichoderma harzianum (CGMCC 7230), is new.    USE - The T.harzianum (CGMCC 7230) is useful for controlling plant pathogenic fungi chosen from Pythium aphanidermatum, Fusarium oxysporum and Botrytis cinerea for preventing and treating plant fungal diseases in melons, fruits, vegetables and crops (all claimed), inhibiting growth of plant pathogenic fungi, and promoting plant growth, and is used independently, or in combination with other organic and inorganic nutrients required for plant growth. The prepared biological fertilizer is useful for promoting growth, and preventing diseases.    ADVANTAGE - The T.harzianum highly inhibits plant pathogenic fungus growth, and causes no environmental pollution, and the prepared biological fertilizer inhibits premature senility, increases yield and improves quality.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) preparation of T.harzianum microbial inoculum involves (a) inoculating T.harzianum in potato dextrose (PD) liquid culture medium 25-30 degrees C, and shaking at the speed of 125-150 rotations per minute, cultivating 3-4 days, and adjusting the spore concentration to 1x 106 per/ml to obtain two culture medium, and (b) carrying out solid fermentation by adding bran, rice straw, corn powder, and rice hull in a ratio of 12:6:2:1.5 to 1 l triangular flask, adding suitable amount of water until the moisture content of the mixture reaches 100%, sterilizing the mixture, adding 10 ml two culture medium obtained in step (a) to the triangular flask at 25-30 degrees C and fermenting the mixture for 3-4 days; and (2) preparation of biological fertilizer involves (a) mixing the microbial inoculum, organic fertilizer, and macroelement fertilizer in a weight ratio of 2:3:5, where the organic fertilizer is compost or marsh gas fertilizer, and the macroelement fertilizer is nitrogen fertilizer, phosphate fertilizer or potassium fertilizer, or (b) mixing the microbial inoculum, organic fertilizer, and trace element fertilizer in a weight ratio of 2:3:5, where the organic fertilizer is compost or marsh gas fertilizer, and the trace element fertilizer is one or more chosen from manganese zinc fertilizer, boric magnesium fertilizer, sodium molybdate fertilizer, copper chelate fertilizer and ferrous ammonium phosphate fertilizer.