This study aims to research the relative humidity (RH) effect of the cellulose filter media loading. The filter loading characteristics of test particles under various RHs (15%, 30%, 45%, 60%, and 75%) are evaluated. Besides commonly used potassium chloride particles, ammonium sulfate and ammonium nitrite, which are the most abundant salts in the atmosphere, are also employed as testing particles to better represent the particle hygroscopic property in the ambient. It was found for certain testing particles, the higher the loading RH, the greater the filter holding capacity. Moreover, the loading characteristics of the three salts vary from each other even at same loading RH. The holding capacity of ammonium nitrate was much greater than those of potassium chloride and ammonium sulfate, because of its special hygroscopic property; while the holding capacity of ammonium sulfate is comparable but slightly greater than that of potassium chloride, which can be explained by its lower deliquescent RH, in other words, higher hygroscopicity.