In seeking for alternatives of potash fertilizer, a strain of potassium-dissolving bacteria coded as G4 was isolated from the red earth in Jiangxi Province. The strain of bacteria is very efficient in dissolving potassium, reaching 27.62% in potassium dissolving rate. G4 was tentatively identified as Paenibacillus sp. based on its morphological, physiological and biochemical features and its 16S rDNA sequence analysis. A single factor experiment and an orthogonal experiment was performed on the strain and found its optimal incubation conditions were maltose 1% (w/v), peptone 0.2% (w/v), dipotassium hydrogen phosphate 0.05% (w/v), temperature 25 ℃, initial pH 7.5, medium volume 80 ml in a 250 ml flask, duration of the incubation 48 h and inoculation rate 7%. Strain G4 is quite good at dissolving potassium, and has the potential to be used in development of microbial fertilizer.