In this paper， the steady-state current-carrying capacity and impact current-carrying capacity of the flexible PCB cable inside a micro aircraft are calculated and designed theoretically. By the MIL-STD-275 standard and empirical formula， the steady-state current-carrying capacity of the flexible PCB cable is reviewed and calculated. With reference to GJB 4057-2000， the impact current-carrying capacity of the flexible PCB cable is estimated. For the theoretical calculation and estimation， the steady-state current-carrying test under the condition of twice the theoretical value and the pulse current test under the condition of 10 times the theoretical value are designed. The test results are consistent with the expected ones， which verifies the correctness of the theoretical calculation. In the current-carrying capacity test， the temperature of the flexible PCB under the current-carrying state of each current value is obtained， and the thermal simulation is carried out by Flotherm software for verification. The stable temperature of the flexible PCB under each current value state is simulated. The thermal simulation results conform to the actual test results， which verifies the authenticity and rationality of the experimental data. The results of the current-carrying capacity experiment and simulation data in this paper can provide experimental data support for the design of PCB in micro aircraft for subsequent short-time operation.