A method for measuring and calculating the radiation emission index of linear oblique polarization radar is proposed in this paper. The actual amplitude of each frequency of the oblique polarization radar at any unknown angle can be quickly measured and calculated by using a single combination of the receiving antenna orthogonal measurement， and then the harmonic and spurious suppression degree of the oblique polarization radar can be calculated. The accurate polarization angle of each frequency point of an arbitrary oblique polarization radar can be quickly measured and calculated with the three frequency-domain combined measurement results of a set of X-axis symmetric angles and three polarization directions of 0 degrees. The proposed measurement and calculation method can effectively avoid the shortcomings of the current radar radiation emission measurement method for the oblique polarization radar. The measurement efficiency is high and the error is small. The test results prove the correctness and accuracy of the proposed method.