The effect of a modified ester collector named as BL on the flotation of chalcopyrite at low temperatures was investigated by micro-flotation tests, contact angle measurements, adsorption experiments, laser particle size analysis, cryogenic transmission electron microscopy (Cryo-TEM) and Fourier transform infrared (FTIR) analyses. Micro-flotation tests proved that the collecting ability of BL for chalcopyrite was significantly better than that of N,N-diethyl dithiocarbamate propiononitrile ester (ester-105) at low temperatures. Combined with laser particle size, Cryo-TEM and FTIR analyses, it was found that the particle size of BL in water was smaller than that of ester-105, and the distributed density of BL was higher than that of ester-105 at low temperatures, indicating that BL dispersed well at low temperatures. Therefore, BL was more easily adsorbed on the chalcopyrite surface and improved the surface hydrophobic degree of chalcopyrite, which were also confirmed by the contact angle measurements and adsorption experiments.