The measurement principle of the x ray double crystal diffraction is introduced in this paper. The positive and negative mismatch from the semiconductor thin layers with the heterostructures

the minibends of crystal chips

the symmetry on the rocking curves

the resolution of the complex curves

and interference fringes are discussed and analyzed.We show that it is important of the measuring results of x ray double crystal diffraction for MOCVD

LPE technology improvements.