This paper investigates the influences of a semiconductor laser with narrow linewidth on a fibre-optic distributed disturbance sensor based on Mach-Zehnder interferometer.It establishes an effective numerical model to describe the noises and linewidth of a semiconductor laser,taking into account their correlations.Simulation shows that frequency noise has great influences on location errors and their relationship is numerically investigated.Accordingly,there is need to determine the linewidth of the laser less than a threshold and obtain the least location errors.Furthermore,experiments are performed by a sensor prototype using three semiconductor lasers with different linewidths,respectively,with polarization maintaining optical fibres and couplers to eliminate the polarization induced noises and fading.The agreement of simulation with experimental results means that the proposed numerical model can make a comprehensive description of the noise behaviour of a semiconductor laser.The conclusion is useful for choosing a laser source for fibre-optic distributed disturbance sensor to achieve optimized location accuracy.What is more,the proposed numerical model can be widely used for analysing influences of semiconductor lasers on other sensing,communication and optical signal processing systems. This paper investigates the influences of a semiconductor laser with narrow linewidth on a fiber-optic distributed disturbance sensor based on Mach-Zehnder interferometer. Is established an effective numerical model to describe the noises and linewidth of a semiconductor laser, taking into account their correlations. Simulation shows that frequency noise has great influences on location errors and their relationship is numerically investigated. Accredially, there is need to determine the linewidth of the laser less than a threshold and obtain the least location errors. Future, experiments are performed by a sensor prototype using three semiconductor lasers with different linewidths, respectively, with polarization maintaining optical fibers and couplers to eliminate the polarization induced noises and fading. agreement with simulation with experimental results that the proposed numerical model can make a comprehensive description of the noise behavior of a semiconductor laser.The c onclusion is useful for choosing a laser source for fiber-optic distributed disturbance sensor to achieve optimized location accuracy. What is more, the proposed numerical model can be widely used for analysing influences of semiconductor lasers on other sensing, communication and optical signal processing systems.