An exteal cavity quantum cascade laser (QCL) array with a wide tuning range and high output power is presented.The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configuration.Taking advantage of the single-lobed fundamental supermode far-field patte,the tuning capa bility of 30.6 cm 1 is achieved with a fixed injected current of 3.5 A at room temperature.Single-mode emission can be observed in the entire process.The maximum single-mode output power of the exteal cavity setup is as high as 25mW and is essential in real applications.