The invention provides a sludge ceramsite for heavy metal wastewater treatment, and a preparation method thereof. The sludge ceramsite is porous ceramsite prepared by pelletizing and sintering mixed raw materials of river sediment, fly ash, vermiculite powder, clay and ammonium bicarbonate, mixing humic acid, isopropanol, sodium carbonate, sodium dodecyl benzene sulfonate, absolute ethyl alcohol and deionized water are mixed to prepare a mixed solution, grinding to form a slurry, and repeatedly soaking the porous ceramsite in the slurry liquid and drying. According to the modified sludge ceramsite provided by the invention, humic acid is used for modifying the ceramsite, so the specific surface area is large, the modified sludge ceramsite has very strong adsorbability to heavy metals Pb, Cd, Cu and the like and stable adsorption rate, can be recycled for multiple times, does not cause secondary pollution, can be widely applied to heavy metal wastewater treatment, and realizes resourceutilization of river sediment, and the purpose of treating waste with waste is achieved.