The invention relates to the field of metal surface treatment, in particular to a low-temperature liquid boronizing agent and a boronizing process. The low-temperature liquid boronizing agent comprises, by mass, 25%-45% of borax, 2%-4% of potassium fluoborate, 0.4%-0.6% of cerium chloride and the balance water. Compared with the prior art, the low-temperature liquid boronizing agent and the boronizing process have the beneficial effects that after co-penetration, workpiece deformation is smaller, phase change and internal stress are avoided, and application of the low-temperature liquid boronizing agent to a precision part is greatly promoted; a low-temperature co-penetration layer is thicker and about 70-80 [mu]m, and the application field is wide; the activity of boron atoms in the liquid boronizing agent is improved, the diffusion rate is increased, and the economy is good; and the cerium chloride for catalyzing penetration is added, and the boronizing temperature can be effectively lowered.