Background: The environmental conditions potentially predispose the northern part of the Persian Gulf to the occurrence of dust storms. Outdoor PM2.5 and their water-soluble ions in Bushehr port were studied from December 2016 to September 2017. Methods: A total of 46 outdoor PM2.5 samples were collected by high-volume air sampler and eight water-soluble ions, including Ca2+, Mg2+, Na+, K+, F- , Cl- , NO3 - , and SO4 2- in PM2.5 were also measured by ion chromatography (IC). Results: The 24-hour average concentration of PM2.5 was in the range of 22.09 to 292.45 µg/m3 . The mean concentration of water-soluble ions in PM2.5 was in the range of 0.10±0.14 to 6.76±4.63 µg/m3 . The major water-soluble ions were the secondary inorganic aerosols (SO4 2- and NO3 - ), which accounted for nearly 41% of total water-soluble ions in PM2.5. The total water-soluble ions level of PM2.5 in winter was higher than that in spring and summer. The positive matrix factorization (PMF) model showed that the source contributions of PM2.5 were in the order of dust (55.8%), sea salt (17.1%), secondary sulfate (11.8%), industries (7%), vehicular emission (4.7%), and secondary nitrate (3.7%). Conclusion: According to the results, dust and sea salt are the main sources of water-soluble ions in PM2.5 in Bushehr port, which should attract much attention.