By using a unique hydrothermal hot-press (HHP) technique, ZnO and ZnO/SnO2 composite porous nanosolids (the content of SnO2 is 0, 1, 5 and 10 wt.%, respectively) were prepared. Furthermore, four kinds of gas sensors were fabricated by using ZnO (the sensor denoted as ZS0) and ZnO/SnO2 composite (denoted as ZS1, ZS5 and ZS10 respectively) porous nanosolids. The intrinsic resistance and gas sensing performance of sensors ZS0, ZS1, ZS5 and ZS10 to ethanol and acetone were tested. By comparing with that of ZS0, the sensors ZS1, ZS5 and ZS10 have obviously lower intrinsic resistance and working temperature, and their selectivity to ethanol was also improved. The reason for above results has been analyzed on the basis of micro-morphology observations.