The invention belongs to the technical field of microbial oil recovery, and in particular relates to a microbial in-situ sand consolidation method for a loose sandstone reservoir. The method comprisesthe following steps: screening a test block; preliminarily determining sand consolidation functional microorganisms and nutrients thereof; preliminarily determining sand consolidation functional microorganisms and nutrients thereof; preliminarily determining sand consolidation functional microorganisms and the injection amount of nutrients thereof; determining sand consolidation functional microorganisms and the injection amount of nutrients thereof; determining sand consolidation functional microorganisms and the injection rate of nutrients thereof; and carrying out on-site implementation and effect evaluation. The microbial in-situ sand consolidation method has the advantages of being reasonable, simple in process, easy to operate, safe and reliable, few in input and low in cost. Meanwhile, the sand production rate of the loose sandstone reservoir can be reduced effectively, the period of validity is prolonged and the liquid production capacity is improved, the sand production rateof an oil well is reduced by over 95%, the period of validity is over 3 years, and meanwhile, the liquid production capacity of the block is improved by over 100%. Therefore, the microbial in-situ sand consolidation method has a wide on-site application prospect.