Hexagonal WO3 nanorods and orthorhombic WO3 nanoparticles were prepared by a simple hydrothermal method with Na2WO4·2H2O and hydrochloric acid as raw materials, and then WO3 was prepared into gas sensor by a screen printing method. The gas sensitivity of the sensor was investigated in the H2 concentration range from 5 to 100 μL/L at 200, 250, 300 and 350 oC. The results show that the sensitivity, stability and response-restoring characteristics of the H2 gas sensors are all excellent. When n(Na2WO4·2H2O):n(HCl) = 1:2, the sensitivity and stability of the product are the highest. And the sensitivity of the H2 gas sensor gradually ascends as the temperature and the H2 concentration are increased.