We investigated preliminarilly the synthesis and crystallization in the system TeO2-K3PO4-H2O under hydrothermal conditions. It was found that in addition to the crystals of TeO2, crystals of a new phase which we called γ could be obtained in the given range of constituent and growth conditions. The γ crystal belongs to trigonal system with α= b=10.734 ?, c=21.041?, α=β=90°, γ=120°. The formula of γ is K2Te4O9·3H2O. Furthermore,it was shown that the crystallized product in the crystallization zone depends mainly on the molar ratio of starting materials k=TeO2/K3PO4 in the system. When k≤1.90, the crystallized phase only consists of γ crystals, k≥2.22, only TeO2 crystals appears, while 1.902 are present together.Finally, the DTA curve and the relative intensities and corresponding d-values of X-ray powder diffraction pattern of γ-phase are also given.