In order to excavate the functional endophyte fungi resources, a fungus strain, named WJ007 with high-efficiency potassium solubilization and desilication was screened from Stenoloma chusanum, it was identified as Penicillium spinulosum based on morphological characteristics, rDNA ITS sequence and phylogenetic relationships analyses. Its optimal culture conditions obtained by single factor and orthogonal experimens for desiliconization were glucose as carbon source, yeast extract as nitrogen source, carbon and nitrogen ratio of 60∶1, initial pH 6, and culture soluble silicon content in liquid is 8.74 mg/L under these conditions; while its optimal culture conditions for potassium solubilization were glucose as carbon source, protein peptone as nitrogen source, carbon and nitrogen ratio of 60∶1, initial pH 7, and soluble potassium contents in culture solution is 154.44 mg/L under these conditions. It is significant for the development and utilization of plant endophytic fungi to optimize fermentation conditions of potassium solubilization and desiliconization for WJ007.