The invention provides a signal transmission circuit which comprises a voltage switching circuit, a current switching circuit and a voltage-stabilized power supply circuit, wherein a power supply for the operation of the signal transmission circuit is provided by a gathering plate, after the power supply provided by the gathering plate passes through the voltage-stabilized power supply circuit, astable operational power supply is obtained; the voltage-stabilized power supply circuit is electrically connected with the voltage switching circuit and the current switching circuit and used for providing stable power supply required in operation; the voltage switching circuit receives current signals transmitted by a sensor in a gathering module, and voltage signals are output to the current switching circuit after amplification and full-wave rectification are carried out on the current signals; and the current switching circuit outputs the current signals to the gathering plate after filtering and conversion are carried out on the voltage signals. The signal transmission circuit has the advantages of scientific design, high practicability, and capability of reducing the loss of current output signals on the circuit effectively.