Pyrite whisker is a special crystallization type. Laser microscope was applied in three-dimensional observation to study different parts of pyrite whiskers occurred in the barite crystal which was discovered in Gengzhuang. The data indicates that the scales of crystal whiskers vary sharply in different parts. The length usually ranges from 150 μm to 1700 μm, the diameter ranges from 3.504μm to 113.720μm. and the degree of surface undulation rises from 0.349μm to 35.128μm. From region a to region d, it shows a law that the variation range of the lengths of the crystal whiskers reduces gradually, in the same way, diameters of crystal whiskers are decreased, and the degree of surface undulation becomes low. We combined the occurrence of crystal whiskers, the study results of paragenetic fluid inclusion of barite, the EPMA data component analysis; we analyzed the relationships synthetically among the features of crystal whiskers, and hydrothermal solution state and the process of evolution. We considered that the huge crystal whiskers with relatively low ratio between length and diameter, surface strumae and high impurity content is the feature symbol of comparatively high temperature and high concentration conditions, and represents an unstable growth environment. The feature guidance of appreciable temperature fluctuations, high component concentration and the unstable state are diameter variances and complex features. The feature guidance of the inappreciable temperature fluctuations, low component concentration and stable state is of small or equal diameter and simple feature. The increased diameter of the crystal whiskers indicates that there is a pulsating and repeated process in the hydrothermal solution process. The characteristic of crystal whiskers is a sign of hydrothermal activity and offers the morphology evidence when doing research on hydrothermal solution state and the process of evolution.