NOVELTY - Preparation method of agriculturally efficient solid nitrogen bacteria product involves screening roots of sea buckthorn tree which are resistant to harsh environments, collecting bacteria from the roots by separating by diluting or crossing, purifying bacteria and culturing in slant culture tubes without nitrogen at pH of 6.8-7.8, and incubating culture tubes in an incubator at 25-30 degrees C for 3 days.    USE - The method is useful for preparing agriculturally efficient solid nitrogen bacteria product (claimed).    ADVANTAGE - The method prepares agriculturally efficient solid nitrogen bacteria product which has yield of 84 billion bacteria/g and reduced urea content, reduces nitrate pollution in soil, is environmentally-friendly and beneficial to people's health, and provides promising nitrogen-fixation.    DETAILED DESCRIPTION - Preparation method of agriculturally efficient solid nitrogen bacteria product involves screening roots of sea buckthorn tree which are resistant to harsh environments, collecting bacteria from the roots by separating by diluting or crossing, purifying bacteria and culturing in slant culture tubes without nitrogen at pH of 6.8-7.8, incubating culture tubes in an incubator at 25-30 degrees C for 3 days, transferring incubated slant culture to 300 ml triangular flask containing 100 ml amino acid agent (10%), culturing mixture using a shaker at 25-30 degrees C and 110 revolutions/minute for 3 days, transferring 100 ml culture into 3000 ml brown bottle containing 10% fulvic acid (1000 ml, molecular weight of 400-1000), culturing mixture in brown bottle using shaker at 25-30 degrees C for 3 days, mixing culture, weathered coal and sterile water in a ratio of 1:70:29, and placing mixture in a greenhouse and fermenting at 25-30 degrees C and humidity of 75-85% for 3 days, where weathered coal is a carrier, carrier is chosen from weathered coal, lignite, peat and crushed straw, culture and carrier are mixed in a weight ratio of 1:100, and mixing with 20 wt.% water.