Water softener

The invention provides a water softener. The water softener comprises a salt box, a light source, a photosensitive condition detection device, a control panel and a display panel, wherein the bottom of the salt box is provided with salt, at least part of the salt is dissolved in water to form salt water, and the salt water is used for regenerating ion exchange resin of the water softener; the light source is arranged at the upper part of the salt box and is used for illuminating the interior of the salt box; the photosensitive condition detection device is arranged in the salt box and is usedfor acquiring an image of an illumination distribution condition in the salt box; the control panel is configured to calculate the residual salt amount of the water softener based on the image obtained by the photosensitive condition detection device; and the display panel is used for displaying the residual salt amount. According to the water softener, the photosensitive condition detection device is arranged to collect