High speed swept testing system plays an important role in the fields of computing first network, 5Gfront haul network, and a new generation of reconfigure-able optical division multiplexing system, etc. The performance of the whole high speed swept testing system basically depends on the characteristics of the laser. To this end, based on the InGaAsP/InP gain chip’s excellent wide spectrum and Littman-Metcalf external-cavity feedback operating principle, a tunable laser with wide tuning range, high scanning speed and mode-hopping free is designed.In experiment, the maximum scanning speed of 240 nm/s, minimum step trigger interval of 0.001 nm, wavelength stability of better than ±1.3 pm/1 min, absolute wavelength accuracy of less than 2.39 pm, power stability of better than ±0.02 dB/1 min, and single longitudinal mode tunable output of 110 nm with mode-hopping free are realized.This study is helpful to promote the research process of the high speed swept testing system, and boost the testing accuracy and the testing efficiency of wavelength division multiplexing devices.