A hostless parking sensor system comprises two to four sensors and a warning device, wherein each sensor comprises an ID pin, a grounding pin, a data pin and a power pin, the data pin of each sensor is connected with a communication bus, the grounding pin and the power pin of each sensor are connected with a grounding line and a power line respectively, one sensor serves as the main sensor, and other sensors serve as auxiliary sensors; the ID pin of the main sensor is connected with the warning device, the ID pins of the auxiliary sensors are connected with the grounding line or the communication buses or not wired, and the sensors allocate addresses to themselves according to the wiring states of the ID pins of themselves. According to the system, the main sensor is connected with the auxiliary sensors in parallel, so that normal work of other sensors is not affected when any auxiliary sensor fails; the main sensor acquires the operating states of the auxiliary sensors in real time, so that the position of the auxiliary sensor which fails is judged accurately after the auxiliary sensor fails.