An actinomycete strain P-13, with antimicrobial activity against muskmelon bacterial spot pathogens, was isolated from the muskmelon rhizosphere soil samples in Xinjiang. The strain P-13 was identified as Streptomyces rochei based on morphological, physiological characteristics and 16S rRNA sequence analysis. The agar diffusion bioassay showed that the diameter of inhibition zone against Acidovorax avenae subsp. citrull BFB and Pseudomonas syringae pv. Lachrymans P4 was above 19 mm and 17 mm, respectively. The antimicrobial substances obtained from strain P-13 were demonstrated to be alkaline and water-soluble compounds according to paper chromatogram analysis and exocellular metabolites. Furthermore, it was stable to be treated by 100°C for 10 min, pH 6 for 6 h, or ultraviolet treatment for 7 h. Moreover, it was insoluble in organic solvents, such as petroleum benzine, diethyl ether, and acetic ether.