The present invention provides a chemical sensor comprising a substrate, a first colorimetric sensor array exposed and arranged in a first accommodating space of the substrate and a second colorimetric sensor array arranged in a second accommodating space of the substrate. The second accommodating space is covered with an isolating layer to isolates liquid molecules but allows gas molecules to pass through. The first colorimetric sensor array changes from a first initial color to a first indicating color according to a volatile part and a non-volatile part of an analyte, and the second colorimetric sensor array changes from a second initial color to a second indicating color according to the volatile part of the analyte, so that information of the volatile part and the non-volatile part of the analyte can be obtained simultaneously.