NOVELTY - Mixed microbial inoculum comprises a fermentation bacterial liquid mixture of Trichoderma viride, Bacillus subtilis, Pseudomonas putida, Bacillus licheniformis and Alcaligenes.    USE - The inoculum is useful for producing marsh gas in a marsh gas tank under low temperature conditions in Northeast China.    ADVANTAGE - The inoculum can be normally used in marsh gas tank during winter in Northeast China.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing the mixed microbial inoculum, comprising (a) preparing Trichoderma viride bacterial liquid by using potato dextrose agar (PDA) culture medium for seed culture activation, fermenting at 28-30 degrees C under a rotational speed of 200 rotations/minute and aeration rate of 1:1 (vol.: vol./minute with the volume ratio of fermentation broth), and culturing to logarithmic growth phase, where the liquid culture medium (fermentation culture medium) of pH 5.3-3.7 comprises (in g) wheat bran (5), rice bran (12), ammonium sulfate (2), potassium dihydrogen phosphate (1), calcium chloride (1), glucose (6) and tap water (1000 ml); (b) preparing Bacillus subtilis bacterial liquid by collecting the activated strain culture, fermenting at 23-26 degrees C under a rotational speed of 150 rotations/minute and aeration rate of 1:1 (vol.: vol./minute with the volume ratio of fermentation broth), and culturing to logarithmic growth phase, where the fermentation culture medium of 7.2-7.4 pH comprises (in g) beef extract (3), peptone (10), sodium chloride (5), tap water (1000 ml); (c) preparing Pseudomonas putida bacterial liquid by collecting the activated strain culture, fermenting at 23-26 degrees C under a rotational speed of 160 rotations/minute and aeration rate of 1:1 (vol.: vol./minute with the volume ratio of fermentation broth), and culturing to logarithmic growth phase, where the fermentation culture medium comprises the components as same as the components of culture medium in the step (b) ; (d) preparing Bacillus licheniformis bacterial liquid by collecting the activated strain culture, fermenting at 25-30 degrees C under a rotational speed of 200 rotations/minute and aeration rate of 1:1 (vol.: vol./minute with the volume ratio of fermentation broth), and culturing to logarithmic growth phase, where the fermentation culture medium comprises the components as same as step (c) culture medium and the pH of the medium is 7; (e) preparing Alcaligenes bacterial liquid by collecting the activated strain culture, fermenting at 28-30 degrees C under a rotational speed of 200 rotations/minute and aeration rate of 1:1 (vol.: vol./minute with the volume ratio of fermentation broth), and culturing to logarithmic growth phase, where the fermentation culture medium of pH 8 comprises (in g) ammonium sulfate (2), sodium chloride (10.15), potassium dihydrogen phosphate (2), peptone (5), glucose (10), yeast extract (5) and tap water (1000 ml); and (f) mixing the five kinds of microorganism bacterial liquids, or adding adsorbent into the mixed liquid microbial inoculum to obtain solid microbial inoculum dosage form, or adding a protection agent into mixed liquid microbial inoculum, performing low temperature vacuum dehydration and drying to obtain the dormant state dry powder.