The invention discloses a bilateral DC insulation detection method and system. The system comprises a detection circuit, a voltage sampling circuit and a processing module, wherein the detection circuit is used for adopting an unbalanced bridge mode to set detection resistors with different resistance values between a positive pole and a ground wire and between a negative pole and the ground wire;the voltage sampling circuit is used for acquiring the detection voltage on all detection resistors; and the processing module is used for calculating leakage resistance between the positive pole ofa charging pile output DC power source and the ground wire and/or between the negative pole and the ground wire based on a preset algorithm and received detection voltage. Through setting detection resistors with different resistance values between the positive pole and the ground wire and between the negative pole and the ground wire by adopting the unbalanced bridge mode, the occurrence of misjudgment of the existing bilateral insulation detection can be avoided, insulation detection of unilateral and bilateral leakage can further be met, the application range is wide, and the insulation detection reliability is also ensured; and besides, the deviation of the calculated leakage resistance is also reduced by linear fitting, and the accuracy of the judgment is improved.