The invention provides an automatic measuring method and device for concentration of saline fog. The method comprises the following steps: S1: a deionized water generating device generates deionized water and a control calculating system controls a peristaltic pump to quantitatively inject the deionized water into porous glass plate absorption tube serial units, separately; S2: the control calculating system controls an air pump to exhaust air to collect a saline fog sample, measures the volume of the sample by means of a gas flowmeter and collects gas data by means of a sensor; S3: the control calculating system controls an absorption liquids in the porous glass plate absorption tube serial units to be guided into a chloride ion concentration measuring chamber to measure the chloride ion concentration in the adsorption liquids by taking a chloride ion sensor as a detection apparatus; and S4: the control calculating system calculates the concentration of saline fog. The method and device provided by the invention can automatically and digitally measure the environmental concentration of saline fog and have the advantages of being efficient, convenient, environmental-friendly, safe and the like.