Novel corncob-derived solid acid catalysts, which used corncob as a precursor, were successfully synthesized for the first time by hydrothermal method under saline condition. The effects of different preparation parameters on the catalytic activity of the corncob-derived solid acid were investigated by using the esterification reaction of oleic acid with methanol. The structure-function relationships of the resulting catalysts were also discussed in detail on the basis of the analysis of structure and composition. Then, the catalytic activity of the resulting solid acid was investigated by using the esterification reaction of waste cooking oil with high acid value. The results indicated that the presence of ZnCl2 yielded a preferable carbonaceous structure composed of polycyclic aromatic carbon sheets in short carbonization time. Compared with the conventional method, the carbonized rate of corncob under saline conditions was increased by 1 time, which also produced a suitable structure for sulfonation process. The resulting solid acid possessed high SO3H density, which caused 4.5 times higher esterification yield of methyl oleate than the solid acid prepared by conventional hydrothermal method. Moreover, the corncob-derived catalyst synthesized under optimized saline conditions exhibited higher catalytic activity in esterification reactions of waste cooking oil, yielding 90.23% fatty acid methyl ester in only 4h.