The invention discloses a method for preparing an inorganic potassium salt based on sugar making diethyl ether and dilute juice desalination. The method comprises the following steps of: (1) eluting a resin bed with sodium strong acid cation exchange resin and diethyl ether to obtain potassium-saturated depotassication resin and depotassication diethyl ether; (2) eluting the resin bed with the depotassication resin obtained in the step (1) and a sodium sulfate solution to obtain sodium strong acid cation exchange resin and potassium-containing eluent; (3) eluting the resin bed with the sodiumstrong acid cation exchange resin and sugar making dilute juice to obtain calcium-saturated decalcification resin and decalcification dilute juice; (4) eluting the resin bed with the calcium-saturated decalcification resin obtained in the step (3) and the depotassication diethyl ether obtained in the step (1) to obtain sodium strong acid cation exchange resin and depotassication sodium diethyl ether; and (5) preparing an inorganic potassium salt from the potassium-containing eluent. According to the method, the content of potassium and sodium in the diethyl ether and the content of calcium inthe dilute juice are lowered, the scaling of an evaporating pot is reduced, and a crystallized inorganic potassium salt with a high added value is prepared simultaneously.