The chaotic repeater is proposed for long-haul chaotic communications. The physical model of all optical chaotic semiconductor laser repeater is presented. The synchronization of chaos repeater system is theoretically demonstrated. Chaos synchronization of a transmitter, a repeater and a recoverer is numerically achieved. Relationships of synchronization error and synchronization time with the system feedback coefficient are analyzed. Application of the repeater system is numerically simulated in chaotic laser communications. Chaotic communications and synchronization error analysis with a sinusoidal modulation signal of frequency 0.2GHz and a digital signal of 0.2Gb/s rate are given respectively to illustrate that chaotic repeater can improve the decoding quality in chaotic laser communications. The repeater bandwidth, chaotic communications with a high rate digital signal of 20Gb/s and synchronization error are analyzed respectively. Numerical results of a sinusoidal modulation signal of bandwidth from 0.1 to 20GHz, and a digital signal of modulation bandwidth from 0.1 to 20Gb/s are obtained, and numerical relationship of synchronization error to the modulation frequency is also shown. The system parameter mismatch is also numerically analyzed.