The invention discloses an aluminum oxide concentration control method based on an aluminum electrolytic cell. The method comprises the following steps that a model is firstly built; then the electrolyte sampling density and sampling temperature are collected; digital filtering is carried out on the sampling density, density compensation is carried out based on the temperature after the weighted mean of the sampling density is calculated, and an equivalent density value is obtained; a control unit obtains an aluminum oxide concentration value according to a concentration/density relation curve; and finally the control unit controls a cell control machine to carry out feeding towards the electrolytic cell according to the aluminum oxide concentration. According to the novel aluminum oxide concentration monitor method, compared with the prior art, the material input quantity can be controlled precisely in real time, and the aim of precisely controlling the aluminum oxide concentration is achieved.