A field sampling, isolation and power detection system of a signal of a low-voltage power line effectively isolates the carrier signal from the power line, and samples and detects the carrier signal. An isolation and sampling module attenuates the signal to an extent suitable for power detection for output, an intermediate-frequency receiver module processes the signal; a controllable digital synthesizer sets local oscillation signal outputs in corresponding frequencies through a processor according to different carrier frequencies; and a receiving signal intensity indication output end of the intermediate-frequency receiver module outputs signal intensity to the processor for processing. The system simply, conveniently and efficiently solves the problem that field carrier communication terminal equipment cannot receive the carrier signal correctly since the carrier signal has attenuation and the like during transmission and is susceptible to the interference of a field electromagnetic environment in a power carrier communication system. With the adoption of the system, field workers can measure and judge the power of the carrier signal in the field electromagnetic environment and on the power line conveniently, and the detection of the power of the carrier signal is realized.