Abstract: The present invention relates to a mercury-containing wastewater treatment technology field, in particular to an attapulgite-crosslinked chitosan composite adsorbent and its solid-phase synthetic method. The attapulgite-crosslinked chitosan composite mercury adsorbent in the invention is synthesized by the method of adding chitosan and glutaraldehyde in batches. In consideration of the limited solubility of chitosan, batch addition can not only dissolve chitosan, but also minimize the use of organic acid, resulting in less discharge of wastewater and waste gas, which is suitable for large-scale industrial production. The prepared mercury adsorbent can be applied to the removal of mercury ions in the wastewater owing to the excellent adsorptive property and regeneration performance. Meanwhile, the solid-phase synthetic procedure for preparing the mercury adsorbent is simple, easy to handle and environmental-friendly. Moreover, the product cost is greatly reduced due to the use of attapulgite.