An effective technology of hydrothermal synthesizing flower-sphere MoS2 by reaction of Na2MoO4 and CS(NH2)2 with NH2OH•HCl as reductant was researched. The effect of the molar ratio of Mo to S, reaction temperature, reaction time, aging time on the yield, purity and morphology of the product was explored by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the optimal synthesis conditions are as follows: the molar ratio of Mo to S of 1:7, the temperature of 220°C, the reaction time of 24h and the aging time of 16h. Under these conditions, the inerratic and pure flower-sphere MoS2 was obtained. Its average particle size is about 2μm and the petal is self-assembly growth. The yield of the product can reach 88%.