Abstract: Operating principle and physical characteristics of capillary X-ray lens are introduced. Using the slightly focusing X-ray lens in the four circle X-ray diffractometers,contrast experiment of crystal compounds with different diameter (0.6,0.4 and 0.2 mm) was conducted. The results showed that when diffraction resolution and precision satisfied the requirements of experiments,the diffracted intensities of three crystals mentioned above obtained increase with different degree. And the diffracted intensity of the crystal with 0.2 mm diameter was raised closed to 5 times. In the same time,the residual stresses experimental results of foreign researchers using parallel X-ray lens were introduced.