Nano-sized SnO2 thick films were prepared by a screen-printing method onto Al2O3 substrates. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box as a function of the detection gas. The nano-sized SnO2 thick film sensors were treated in a N2 atmosphere. The structural properties of the nano SnO2 with a rutile structure according to XRD showed a (110) dominant SnO2 peak. The particle size of SnO2:Ni nano powders at Ni 8 wt% was about 45 nm, and the SnO2 particles were found to contain many pores according to the SEM analysis. The sensitivity of the nano SnO2-based sensors was measured for 5 ppm CH4 gas and CH3CH2CH3 gas at room temperature by comparing the resistance in air with that in the target gases. The results showed that the best sensitivity of SnO2:Ni and SnO2:Co sensors for CH4 gas and CH3CH2CH3 gas at room temperature was observed in SnO2:Ni sensors doped with 8 wt% Ni. The response time of the SnO2:Ni gas sensors was 10 seconds and recovery time was 15 seconds for the CH4 and CH3CH2CH3 gases.