The invention discloses a double-channel arc light detection unit. The double-channel arc light detection unit comprises an unit structure body, a light source, a semi-reflecting and semi-transmittingmirror, a light detector, a first focusing lens, a second focusing lens, a first optical fiber connector and a second optical fiber connector, wherein the light source, the semi-reflecting and semi-transmitting mirror, the light detector, the first focusing lens, the second focusing lens, the first optical fiber connector and the second optical fiber connector are all mounted on the unit structure body to form a compact double-channel detection unit structure together. According to the detection unit, the double-channel arc light detection is realized in one unit structure; the quantity of devices in a multi-detector arc light monitoring system can be decreased, so that the cost is decreased, and the system stability is improved; the unit has a self-examining function, so that the systemreliability is further improved.