To meet the requirements of big survey area and rapid exploration of groundairborne frequencydomain electromagnetic method, an aircore sensor (ACS) is developed for GAFEM with high sensitivity, low noise and low weight. First, based on the onedimension forward method, the equivalent area normalized response voltage at 10 km is calculated. And the index requirements for ACS′s sensitivity and noise levels are determined. Then, the circuit model of the sensor is built, and the noise of the aircore sensor is analyzed. Low noise and low weight are achieved by optimizing the design parameters of the sensor through lagrangian multiplier method. Finally, according to the optimized parameters, the aircore coil sensor is designed and fabricated, and the sensor is tested in the electromagnetic shielding room. Results show that the noise of coil at noise reference point (100 Hz) reaches 009 pT/Hz1/2, the sensitivity is 147 mV/nT, and the total weight is 125 kg. In addition, field experiments show that the optimized ACS obtained the magnetic which is consistent with that of the AMTC30 at the same measuring point, and the ACS can acquire effective magnetic data in the practical survey.