Abstract: According to the designed cold neutron guide system and by means of simulating calculation and analyzing, the most important parameters for design were got which are available range of neutron wavelength, flux at the sample position and resolution of energy. Based on these parameters, the specifications of the space layout of the spectrometer and its main components were given out, including transmission range of energy and momentum, angle range and mosaic spread of monochromator and analyzer, scattering angle of the sample table, collimation angle of collimators, and the background and dose.