In order to obtain linear spot that the length can be adjusted continuously,a beam shaping system based on cylindrical microlens array has been designed,which uses two identical cylindrical microlens arrays connected in series,to form uniform linear spot on the image plane through the focusing of Fourier lens. Based on the theory of matrix optics,the imaging ray matrix has been established,and the related factors affecting the spot length have been analyzed. Based on Fourier optics,the mathematical model of light field has been established,and the light intensity distribution characteristics are simulated by numerical analysis method. An experimental system has been built and obtained uniform line spot with flat top distribution,the length of the spot can be continuously adjusted in the range of 2~34 mm. This linear spot with continuously adjustable length has important application value in the field of laser application and can better meet the requirement of actual production.