The invention relates to a communication and power source circuit of a drain pipe network detection device. A power source of a traditional communication and power source circuit has interference to influence the reliability of work. The communication and power source circuit comprises an RS232 communication interface part, a switching circuit part, a voltage acquisition circuit part and a power supply part. The RS232 communication interface part adopts a nine-core socket. The switching circuit part comprises a first operational amplifier, four resistors, a switch diode and an NPN type triode. The voltage acquisition circuit part comprises four switch diodes and two filter capacitors. The power supply part comprises four resistors, an operational amplifier, a PNP type triode and a light-emitting diode. The external power is supplied by a communication lead but not a power source; the communication and power source circuit outputs reliable voltage and has stronger interference resistance. The elements adopted in the communication and power source circuit are matured and reliable, low in cost and rich in sources.