ANCAOLAN is a weed killer, its series product, the crystal Ⅰ(C11H16N2O4 PSCL) and crystal Ⅱ(C12H13P21/c. There are four molecules in a unit cell. The crystal parameters are: crystal Ⅰ α=8.575?, b= 26.541 ?, c= 7.063?,β= 94.744°; crystal Ⅱ α= 8.575?, b= 26.538?, c= 7.073?, β= 93.819°. For the crystals Ⅰ and Ⅱ, the three-dimensional intensity data were collected by using PW-1100 four-circle diffractometer and the numbers of independent diffractions are 3123 and 3166 respectively.Their structures were solved by direct method and refined by full matrix least-squares method. Their final .R-factors are 0.10 and 0.11 respectively.The plane of nitro is perpendicular to the plane of benzene ring.The weed killing effect of crystal Ⅱ is better than that of the crystal Ⅰ.