Thiourea dioxide was prepared by feed of two raw materials thiourea and hydrogen peroxide, during this synthetic process more parameters were consider, such as feed ratios, mother solvent, the volume of solvent, temperature, pH, different kind of additives, the crystal growth time, after think about those conditions more reasonable process was obtained and finally the quality of product and yield were promoted. Experimental results show that the best technological parameters were confirmed, which temperature is 3～5 ℃, pH is 4, the feed ratios of hydrogen peroxide is 6 s/drop, feed ratios of thiourea and hydrogen peroxide is 1.8∶1, water is a good solvent for this process and the using amount is 45 mL, the whole reaction lasting 1.5 h, potassium acetate and ammonium bicarbonate are the prior additives for this reaction, during this process the total cycle index is 1. Based on this process, the final yield was beyond 90%, using water as reaction solvent the target productivity reached to 88%.