The crystal structure of anorthoclase was determined by the single-crystal method quite a few years ago. In this paper, the intensities of reflection were collected with X-ray powder diffractometer, and 474 independent diffractidn data were involved in the calculation, with the final discrepancy factor R=0.114.The ideal formula for the anorthoclase is (Na, K)A1Si308. It is of triclinic system, with the lattice parameters being a=8.267士0.0025A，b=12.954士0.0017A， c= 7.149土0.001A，a=92º12.2'士1.8',β=116º020.4'士1.2', γ = 90º12.1'士1', V=685.4A3， Z=4. A comparison between the result obtained by powder method and that by single-crystel method shows that they are in good agreement with each other and that the band distance and bond angles are on the whole reasonable. Nevertheless, the accuracy of determination requires further improvement.