In this work

Monte Carlo simulations were done for optimization of pre-guide of neutron reflectometer(NR) in two proposals: A

pre-guide of 8.0 m in length

vertical focusing guide of 200-mm entrance and 40-mm exit height;B

pre-guide of(1.6 + 3.4) m long

vertical focusing and horizontal deflecting guide of 100-mm entrance and 50-mm exit height.The following results were found: 1) it is not necessary to deflect neutron beam for NR at the exit of cold neutron guide

2) compared proposal A with B

the flux at pre-guide exit decreases 52.8% and divergence increases 24.1% in horizontal direction and decreases 60.7% in vertical plane

and 3) a optimized pre-guide should not be shorter than 6.0 m

focusing super-mirror factor m in the range between 2.0 and 2.5

and its entrance height no less than 150 mm.