The invention relates to a process for recovering magnesium sulfate monohydrate from boron extraction mother liquor. The process comprises the following steps of: (1) pouring the boron extraction mother liquor with the initial composition of magnesium sulfate with the concentration of 18%-24% and boric acid with the concentration of 0%-4% into an evaporation reaction kettle under normal-pressure conditions, heating till boiling, and keeping the temperature unchanged; slowly increasing the temperature to 102-105 DEG C when the concentration of the boron extraction mother liquor achieves 1.397-1.410g/mL or 41-42 Be'; and continuously heating, and respectively obtaining a concentrated solution and condensed water A when the concentration of the boron extraction mother liquor achieves 1.468-1.483g/mL or 46-47 Be'; (2) transferring the concentrated solution into a crystallizer, and performing constant-temperature evaporation and crystallization to obtain slurry and condensed water B; (3) performing thermal separation on the slurry to obtain a magnesium sulfate monohydrate crude product; washing the magnesium sulfate monohydrate crude product with a mixed solution of the condensed water A and the condensed water B to respectively obtain a wet product and a washing solution; and returning the washing solution to the step (1) for recycling; and (4) drying the wet product till constant weight to obtain the magnesium sulfate monohydrate. The process disclosed by the invention has the characteristics of low energy consumption and low cost.