The influence of different bromomethanol solution etching methods on the surface roughness and Reflection High-Energy Electron Diffraction (RHEED) pattern of CZT(211)B substrate for molecular beam epitaxy were analyzed in this paper.It was found that CZT(211)B substrate which had not been etched with bromomethanol after chemical polishing had a small surface roughness (less than 1.0 nm),but the RHEED pattern had no diffraction spots or stripes.When the CZT(211)B substrate is etched by a 0.05% vol.% bromomethanol solution,even if the etching is extremely short time,the surface roughness of the substrate reaches 2.0 nm or more,and a high-density pillar is present on the surface,and the RHEED patterns are round or thick stripe with bright spots.When the CZT(211)B substrate is etched by a 0.01 vol% bromomethanol solution,The surface roughness can be controlled at about 1.0 nm,and the RHEED pattern is clear short stripes which is the standard diffraction pattern of CZT (211)B crystal face.At the same time,the results of repeated experiments on multiple substrates are consistent.The unoptimized medium-wave HgCdTe material by the MBE on these substrates has a Full Width at Half Maximum (FWHM) of (49.1±5.9)arcsec,a composition of 0.3083±0.0003,and a thickness of (6.54±0.019)μm.