The author introduces a new method (five, axis-twin method) for direct me- asuring of the angle C∧Ngmx, of clinopyroxene on the universal stage. The me- asuring procedure is as follows: 1)selecting some mineral grain; with twinning plane (100) in plane-law twin and putting them in the center of the universal stage; 2) turning N-axis and making it parallel to the longitudinal line; 3) tilting H-axis and making the composition plane of twin coincide with the up- right plane of longitudinal line; 4) setting M-axis at angle 90º for K┴I, and putting plane (O10) of the principal optic axis on the S-N upright plane, so Nm(1,2) coincide with the 1-axis; 5) tilting alternately K-axis and 1-axis, and making successively Np1 Np2 (or Ng2)，Ng1Np2`, and Ng1Ng2 coincide with the K- axis, meanwhile, writing down the readings of 1-axis while the axis of each indicatrix coincides with K-axis; 6) according to the readings on the graduated wheel of 1-axis, calculating the angle of Ng1∧Ng2, then (N1∧Ng2) /2 =C∧Ng. The above-mentioned method widens the application range without the aid of stereographic projection.