A two-track piezoresistive cantilever detects explosives in ambient air by measuring resistance changes in the cantilever when one piezoresistive track is pulse heated to cause deflagration of explosive adhered to the surface of the cantilever. The resistance measurement is through the second piezoresistive track, which is located at the most resistance-sensitive area. The resistance change of this track is caused by the temperature change of the cantilever as well as the bending of the cantilever due to bi-material thermal expansion. The detecting method using this novel cantilever avoids the use of any optical components such as a laser and position sensing detector (PSD), which are necessary in traditional detecting systems using cantilevers. Therefore, it can extremely reduce the complexity of the detecting system and make a portable chemical detection system possible that is small, less expensive, and able to be mass produced and is particularly useful for the detection of explosives.