The disclosure provides low-molecular-ratio cryolite for aluminium electrolytic industry, which consists of potassium cryolite and sodium cryolite with a mole ratio of 1:1˜1:3, wherein the molecular formula of the potassium cryolite is mKF.AlF3 and the molecular formula of the sodium cryolite is nNaF.AlF3, where m=1˜1.5 and n=1˜1.5. When the low-molecular-ratio cryolite provided by the disclosure is applied to the aluminium electrolytic industry, electrolytic temperature and power consumption can be reduced and electrolytic efficiency is improved.