Different samples need different resolution requirements of a neutron reflectometer.To achieve this

a space-adjustable neutron chopper with four disks was designed.The principle is adjusting the disk rotation frequency

according to the space difference from the 2# disk to the 3# and 4# disks.The new design was simulated with Mcstas codes

and the intensity and horizontal divergence as function of different physical parameters in given conditions were obtained.The results provide theoretical basis for designing the four-disk chopper of a horizontal geometry scattering neutron reflectometer.