The invention relates to a method for measuring ore grade, in particular to a method for measuring ore grade by a hydrometer method. The method comprises the following steps: sampling and specific gravity measurement: putting each sample ore into a cage, weighing weight G of each sample ore in the air and weight G' of each sample ore in the water with a weighing machine one by one, inputting the weight data into a spreadsheet document set by a computer, working out specific gravity gamma of each sample ore, checking a specific gravity-ore grade curve by utilizing the worked out ore specific gravity so as to obtain the grade of the sample ore, working out grade mean value of the ore sample by the weighting method, comparing the average ore grade with the planned ore grade, finally making judgments on ore grade to indicate whether the sample ore is qualified product or not. The method of the invention has simple operation, environment friendliness, energy conservation, less consumption of materials and devices, safe, fast and accurate measurement of ore grade.