With the rapid development of fiber optical communication and fiber to the home,it is urgent to design an optical time domain reflectometer (COTDR) with stable performance,high resolution and low cost for fiber fault detection.In this paper,we propose and demonstrate experimentally and numerically an OTDR using a laser modulated by Boolean chaos to realiz e the fiber fault detection with high precision.The chaotic laser is generated f rom the distributed feedback (DFB) laser diode directly modulated by drive circuit and Boolean chaos.The chaotic laser is divided into two parts through a fiber coupler:one serves as reference light,and the other as probe light which i s sent down to the test fiber. The echo light from the fault and the reference light are converted into electri cal signal and sampled simultaneously.Finally,the fiber fault is detected by correlating the two grou ps of sampling data.Ex- perimental results show that the unterminated fiber end,mismatch connector and fiber breakpoint can be preciously located.A detection range of approximately 98km and a range -independent spatial resolution of 24cm are achieved.The device has a simple structure,low cost,and it is easy to realize integration and product,which is in accordance with the practical re quirements of engineering applications.