To achieve high uniform lighting and different lighting modes on the immersion lithography mask face,the coherent factor adjustment system is established.Laser beam transmission system is an important part in immersion light illumination system for lithography machine,which affects the performance of lithography directly.According to the characteristics of immersion lithography lighting system,the optical structure consists of one spherical lens and two cylindrical mirrors has been put forward.Then,the laser collimation and expansion system has been designed and analyzed.In addition,the tolerances of the system have been analyzed to ensure the divergence angle and aperture diameter meet the design requirements after manufacturing and installing.Finally,the size of spot for different distance have been detected on the basis of the real system.The results show that this system can meet the design requirements of spot size and divergence angle within 5~20 m transmission optical path range without adjusting the interval between lenses,and the target beam diameter is in the range of (28.5±0.5)mm,X-direction divergence angle is of 1.2 mrad,Y-direction divergence angle is of 1.84 mrad.In conclusion,this optical system can satisfy high precision lithographic system,which has higher application values and more practical significances.