This paper made a tentative in-situ nondestructive study of components of single fluid inclusions from No.3 granitic pegmatite vein in Altay of Xinjiang by SRXRF which was generated by beamline 4W1B of Beijing Synchrotron Radiation Facility (BSRF). The authors have improved micro-vedio lightning facility by which better, faster and more precise visual effects could be obtained, and the test results are more reliable. Studies show that most fluid inclusions of No. 3 granitic pegmatite vein have relatively high concentrations of Zn, Sn, As and REE which may be the characteristics of endogenous magmatism and crustal source. Spider diagram shows the similarity between Kektokay No. 3 granitic pegmatite vein and the crust in middle and east China in the concentration style of trace elements, suggesting that the source of the fluid might have been derived from the crust. The relatively large X-ray spot (50 μm×50 μm) might have affected the accuracy of the test, but it can be avoided and the test accuracy can be improved by shrinking the light spot, raising the energy of the beam and enhancing energy resolution of the facility.