The invention discloses a method for circulation production of potassium chloride and sodium chloride and a system. The method comprises the following steps: S1, an evaporation step, namely evaporating raw material brine, and generating a salt ore and carnallite raw ore slurry in a sodium salt tank, an adjusting tank and a carnallite tank; S2, a flotation step, namely, carrying out flotation on the carnallite raw ore slurry in a reverse flotation-cold crystallization device so as to obtain low sodium carnallite and tailings, wherein the low sodium carnallite is used for producing potassium chloride; S3, a hot melting step, namely, dissolving the tailings and a second salt ore as raw materials in a hot melting device so as to obtain sodium-containing ore slurry and a potassium-containing liquid, wherein the potassium-containing liquid is used for producing potassium chloride; S4, a salt washing step, namely, washing the sodium-containing ore slurry and the first salt ore in a salt washing device, collecting a solid phase as a sodium chloride product after washing, and feeding back a liquid phase into the carnallite tank for continuous recycling and reuse. According to the technicalscheme of the invention, the purpose of circulation production of potassium chloride and sodium chloride can be achieved, and resource standby and waste can be avoided.