A SnO2-SiO2 composite fabricated with an EBE method was developed as the sensitive film for a room-temperature SAW H2S in this work. In this film, the SnO2 nanoparticels, acting as the active adsorption sites, were uniformly deposited on the slanted SiO2 nanorods array with a mesoporous structure. This structure is found to be beneficial for adsorption and diffusion of H2S gas molecules, thus leading to an excellent sensing performance of the sensor. The fabricated sensor exhibited a frequency response ranging from −180 Hz to −13550 Hz toward H2S with a concentration varying from 0.05 ppm to 10 ppm and a fast response, good selectivity and stability. In addition, the sensing mechanism of the sensor was revealed to be lied on the change in film mass during the adsorption process.