The invention provides a strain of Penicillium sclerotiorum and its application and belongs to the technical field of microorganisms. The strain of Penicillium sclerotiorum is preserved in the China center for type culture collection and has an accession number of CCTCC No: M2016543. A green tea filtrate is inoculated with the strain and is fermented so that caffeine is reduced and epigallocatechin gallate effects are reduced. The strain of Penicillium sclerotiorum has strong adaptability and high fermentation state controllability and does not produce toxic and harmful substances. The strain of Penicillium sclerotiorum can also be used to prepare tannase-containing low-caffeine weak-bitter taste green tea beverage raw pulp. The invention provides a novel nutrient-rich low-caffeine content tea beverage retaining the original green tea ingredients. The strain of Penicillium sclerotiorum can greatly reduce the bitter taste of the green tea beverage and provides a new thought for production of a tea beverage.