A method combining optical metallograph with rotating orientation X-ray diffraction was applied for the measurement and evaluation of orientation for molybdenum-niobium alloy single crystal quickly and accurately. The diffraction angle of (111) orientation plane measured by this method almost accords with the calculated value. The disorientation angles of the samples are 0.73 o and 0.91o, respectively, which are consistent with the results measured by EBSD. The degree of scatter in the preferred orientation is about 1o