TOA-based ultrasound localization is an important technique for fine-grained location-based services. However, its positioning accuracy is sensitive to indoor environments. When radio signal for time synchronization is interfered or ultrasound propagates in Non-Line-Of-Sight (NLOS) path, the positioning accuracy decreases remarkably. System and algorithms for robust ultrasound TOA positioning are proposed. Firstly, Dragon, a system which uses cable-connected RF (Radio Frequency) + US (UltraSound) receivers is designed to conduct accurate and robust 3D positioning. The RF+US receivers are connected by a syncline, enabling a first-falling-edge synchronization technique, which guarantees robust time synchronization even in severe interference environments.