Calcium- and magnesium-containing salts are important components for mineral dust and sea salt aerosols, but their physicochemical properties are not well understood yet. In this study, the hygroscopic properties of eight Ca- and Mg-containing salts, including Ca(NO 3 ) 2 · 4H 2 O, Mg(NO 3 ) 2 · 6H 2 O, MgCl 2 · 6H 2 O, CaCl 2 · 6H 2 O, Ca(HCOO) 2 , Mg(HCOO) 2 · 2H 2 O, Ca(CH 3 COO) 2 · H 2 O and Mg(CH 3 COO) 2 · 4H 2 O, were systematically investigated using two complementary techniques. A vapor sorption analyzer was used to measure the change of sample mass with relative humidity (RH) under isotherm conditions, and the deliquescence relative humidities (DRH) for temperature in the range of 5–30 °C as well as water-to-solute ratios as a function of RH at 5 and 25 °C were reported for these eight compounds. DRH values showed a large variation for these compounds; for example, at 25 °C the DRH values were measured to be ~ 28.5 % for CaCl 2 · 6H 2 O and > 95 % for Ca(HCOO) 2 and Mg(HCOO) 2 · 2H 2 O. In addition, a humidity-tandem differential analyzer was used to measure the change in mobility diameter with RH (up to 90 %) at room temperature, in order to determine the hygroscopic growth factors of aerosol particles generated by atomizing water solutions of these eight compounds. All the aerosol particles studied in this work, very likely to be amorphous, started to grow at very low RH (as low as 10 %) and showed continuous growth with RH. The hygroscopic growth factors at 90 % RH were found to range from 1.26 ± 0.04 for Ca(HCOO 2 ) 2 and 1.79 ± 0.03 for Ca(NO 3 ) 2 , varying significantly for the eight types of aerosols considered herein. Overall, our work provides a systematical and comprehensive investigation of the hygroscopic properties of these Ca- and Mg-containing salts, largely improving our knowledge in the physicochemical properties of mineral dust and sea salt aerosols.