To address the poor flotation recovery of high–ash fine low–rank coal, this study proposes and validates a hydrophobic agglomeration–flotation process induced by an ester–type collector. Coal slime from the Dongsheng mining area, Inner Mongolia, was used as the research object to comparatively investigate the surface modification and agglomeration behaviors of n–dodecane and methyl laurate, as well as the effect of preconditioning agitation speed on agglomeration–flotation performance. In combination with contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and X–ray photoelectron spectroscopy (XPS), the selective adsorption mechanism of the ester–type collector on the coal surface was elucidated. The results show that the contact angle of the raw coal was only 28.1°; after treatment with n–dodecane, it increased to 41.9° and further to 48.7° following hydrophobic agglomeration, whereas treatment with methyl laurate increased the contact angle to 50.7°, which was further enhanced to 56.6° after hydrophobic agglomeration. In terms of flotation performance, within a dosage range of 1000–4000 g/t, the clean coal yield increased from 19.87% to 27.12% with n–dodecane, while it increased from 41.11% to 58.78% with methyl laurate. When hydrophobic agglomeration was induced by preconditioning with methyl laurate, a stirring speed of 2000 r/min resulted in a clean coal yield of 64.02% with an ash content of approximately 20%. Moreover, the use of a composite reagent system with a methyl laurate to n–dodecane mass ratio of 1:3 achieved a clean coal yield of 61.73%, thereby balancing flotation performance and reagent cost. FTIR analysis revealed a significant reduction in the relative proportion of self–associated hydroxyl groups after methyl laurate treatment, while XPS analysis showed that the proportion of C–O species in the C 1s spectrum decreased to 15.01%, accompanied by a pronounced decrease in C–O species in the O 1s spectrum, indicating that ester–type collectors preferentially interact with oxygen–containing sites such as hydroxyl groups via weak hydrogen bonding and/or dipole–dipole interactions.