Nuclear quadruple resonance (NQR) has been studied for explosive detection for years. Some prototype NQR-based detection systems have been reported, but were all designed from the laboratory perspective, with bulky sizes and high power consumption. To achieve a portable NQR-based detection system for field applications, a low-power compact system utilizing state-of-the-art semiconductor technologies is presented in this paper. Several novel circuits for the key modules are proposed, including a Class-D type power amplifier, a power multiplexing and matching network, a customized IC with integrated analog signal processing chain, and a microcontroller-based logic control unit. An advanced digital signal processor platform is employed for data collecting and processing. The customized IC is fabricated in 0.18 mu m CMOS process. Test results on the prototype system show the effectiveness of the proposed solution and low power consumption as 2.12 W in the receiving state. The power efficiency of the proposed transmitting section is higher than 60%.