NOVELTY - Preparing microbial inoculum comprises adding fresh livestock manure with strain and then adding sterile water and then stirring and centrifuging to obtain supernatant, adding pulverized paper, sodium hydrogen phosphate, potassium hydrogen phosphate, peptone and water in a fermentation tank, fermenting, cooling the fermented mixture, adding supernatant into the fermented mixture, culturing to obtain fermentation seed liquid, crushing crop straw, then adding bran, crushed crop straw, water and urea into a fermentation broth, and stacking the product, turning once for every 5 days.    USE - The method is useful for preparing microbial inoculum (claimed) for promoting mineralization and humification of organic matter, and decomposition of corn straw.    ADVANTAGE - The method is capable of preparing the microbial inoculum with improved quality.    DETAILED DESCRIPTION - Preparing microbial inoculum comprises (a) adding 1000 g of fresh livestock manure with strain and then adding 4000 ml of sterile water, stirring the mixture for 5 minutes and then centrifuging for 10 minutes to obtain supernatant, (b) adding 1000 g of pulverized filter paper, 80 g of sodium hydrogen phosphate, 50 g of potassium hydrogen phosphate, 75 g of peptone and 30 l of water having pH of 6.5-7.5 in a fermentation tank, fermenting at 121 degrees C for 30 minutes, cooling the fermented mixture to 55 plus minus 0.5 degrees C, adding 3500 ml of supernatant into the fermented mixture, maintaining the temperature to 55 plus minus 0.5 degrees C, culturing under speed of 60 revolution per minute for 120 hours to obtain fermentation seed liquid, (c) crushing crop straw into particles with a size of less than 3 mm, then adding bran, crushed crop straw, water and urea into a fermentation broth according to mass ratio of 100:10:40:1:1, stacking the product according to height of 1-1.5 m for 20-25 days, turning once for every five days after stacking to prepare master batch, and (d) crushing the crop straw into particles with size of 10 mm, and repeating the step (c). INDEPENDENT CLAIMS are included for:    (1) whole plant straw stack rotten collecting method, comprising selecting flat area for planting the corn, collecting corn straw, alternately stacking the corn straw into horizontal and vertical order at a total height of 150-180 cm, pressing the straw stack to compact when the thickness of stack is 25-35 cm, uniformly spraying 1.5-3 wt.% of urea and 1-3 wt.% of strain on the corn straw and then stacking, shaping top part of the stack into flat, then covering the stack using a agricultural film cover, pressing the covered stack using rock, applying pressure on the top hole of the stack to compact, supplying rainwater through agricultural film, and composting for 90-120 days; and    (2) plant straw stack collecting structure, comprising a corn planting field, a corn straw stack having total height of 150-180 cm and thickness of 25-35 cm, where the corn straw stack is provided with a straw rotten agent layer, an outside of the straw stack is provided with the agricultural film cover, the top part of agricultural film is pressed with a rock, and lower part is provided with a water hole.