The invention relates to the field of fuel detection, and particularly discloses an analysis method of oxygen and metal atom ratio in an MOX pellet. The method comprises the following steps: step 1, preparation of instruments; step 2, sample treatment; step 3, sample determination; step 4, result calculation. The method realizes accurate determination of O/M in a fast reactor MOX pellet with the content of PuO2 reaching 25 percent, the standard deviation of an O/M measured result is 0.001 to 0.002, and reaches the foreign standard level.