The invention discloses a data signal and DC power source collinear transmission system and method. When the front equipment will send data to the rear equipment, data signals are input into the data receiving end of the front circuit; the front circuit encodes the data input and outputs synchronous PWM signals, to boost PWM signals so that the voltage of PWM signals on the first terminal is higher than that of DC power source; the mixed signals composed of PWM signals and DC power source signals are transmitted to the rear equipment through two-wire system bus; after signals are transmitted to the rear circuit, PWM signals and DC power source signals separate, and DC power source signals are output to DC power source output interface; the rear circuit conducts analysis treatment of synchronous PWM signals input and outputs corresponding data signals. In the invention, the whole system has a centralized power supply and collinear transmission of DC power source and high-speed data signals is realized in the two-wire system, which reduces the quantity of laid cables and system cost in monitoring and control of the system.