The invention discloses a work protection system for a DFB (distributed feed back) laser. A laser diode and a semiconductor refrigerator are arranged in the DFB laser; the work protection system comprises a constant-current protection system and a temperature-constant protection system, wherein the constant-current protection system comprises a constant-current voltage comparison circuit, a switching circuit and a constant-current drive circuit; the constant-temperature protection system comprises a temperature-constant voltage comparison circuit and a temperature-constant drive circuit. The work protection system for the DFB laser has the following benefits: the on/off of the constant-current drive circuit is controlled by arranging the constant-current voltage comparison circuit and the switching circuit, and the on/off of the constant-temperature drive circuit is controlled by arranging the temperature-constant voltage comparison circuit, so that hardware protection is provided for the DFB laser, and the hardware protection responses quickly and works stably; three types of sampling circuits are arranged for monitoring the work of the laser in real time, and the constant-current drive circuit and the constant-temperature drive circuit can be controlled remotely, so that software protection is provided for the DFB laser, and the software protection is convenient to operate.