The present invention discloses a DC charging pile detection system applied to a site and a method. The DC charging pile detection system comprises an acquisition and battery voltage simulation unit, a load unit and a control unit, and the acquisition and battery voltage simulation unit is configured to detect whether a DC charging gun is connected reliably, after the situation that the DC charging gun is connected reliably is confirmed, acquire an AC input voltage and a current signal and an output DC voltage and the current signal, and convert the acquired analog quantity signals into the digital signals, calculate to obtain the input power, the output power, the efficiency and the harmonic numerical value of a DC charging pile and transmit to the control unit. The control unit calculates the efficiency and the power of the DC charging pile, and detects whether the DC charging pile adjusts the output values timely when an external environment changes. According to the present invention, the switching value control needed by the detection stages is realized by using a computer to send the control commands to directly control the relevant relays to turn off or turn on without needing the artificial manual control.