A spinel-reinforced magnesium oxide-based foam ceramic filter, which is obtained by coating a light-burned magnesium oxide-based ceramic slurry containing a nano lanthanum oxide sintering aid on a polyurethane foam carrier, then drying and sintering same. The preparation method for the foam ceramic filter comprises the following steps: (1) according to mass percentage, mixing 15%-25% of nano alumina sol and 0.8%-1.5% of a rheological agent, the rest being magnesium oxide ceramic powder containing a nano lanthanum oxide sintering aid, adding anhydrous ethanol, mixing well by means of ball milling, and obtaining a ceramic slurry having a solid content of 60%-70%; (2) immersing a polyurethane foamed plastic template in the ceramic slurry, pressing the polyurethane foamed plastic template by means of a rolling machine to remove excess immersion slurry, then forming a biscuit, and removing the ethanol solvent in a ventilation chamber at 40°C-50°C to dry the biscuit; (3) placing the dried biscuit in a sintering furnace, raising the temperature to 1350°C-1550°C for high-temperature sintering, and cooling to room temperature in the furnace to obtain a magnesium oxide-based foam ceramic filter.