A low operating temperature and short response/recovery time are essential factors for sensors. Hence, it is necessary to create a sensor that can quickly detect target gas at a relatively low temperature. In this work, Co3O4 microtube based sensors were fabricated by a bio-template method using absorbent cotton. Co3O4 microtube sensors prepared in different concentrations of a salt solution displayed different sensitivities to triethylamine (TEA). The Co3O4-0.10 microtube sensor exhibited excellent sensitivity to TEA at 160 °C. The response of the Co3O4-0.10 sensor to 100 ppm TEA gas was 31.27 and the detection limit of TEA was 50 ppb. Meanwhile, the Co3O4-0.10 sensor also showed a short response/recovery time, such as 95 s/38 s to 100 ppm TEA, high selectivity, a good linear relationship (R2 = 0.994 for 1-100 ppm TEA and R2 = 0.991 for 50-1000 ppb TEA gas), fine repeatability and long-term stability, and strong humidity resistance. Thus, Co3O4 microtube based sensors prepared using a bio-template method have potential application prospects for the detection of TEA gas.