Abstract: A pathogenic fungus named MM-2022 was isolated and purified from the naturally infected Matsucoccus matsumurae 2^nd instar nymph. The strain was identified as Penicillium cairnsense through methods such as back infestation test, morphological observation, and molecular sequencing. A native pathogenic fungus, P. cairnsense, which naturally infected and killed M. matsumurae, has been isolated for the first time. Colony color, texture, and scanning electron microscopy results of P. cairnsense are different on PDA and SDAY culture medium. The colonies of the strain in PDA culture medium showed dark gray-green, powdery or granular texture, while the back of the colonies showed light yellowish-green. Scanning electron microscope of the strain showed plump conidiophore, 2 whorled penicillus, 7–9 bottle-shape phialides, and a large number of globose conidia. However, the colonies of the strain in SDAY culture medium showed bright yellow, fluffy texture, while the back of the colonies showed yellowish-brown or dark yellowish-brown. Scanning electron microscope of the strain showed dry conidiophore, relatively few phialides and conidia. The comparability between the rDNA sequence of strain MM-2022 and P. cairnsense in GenBank is 99%, and these 2 strains are gathered in one branch in the phylogenetic tree.