Amino functional silica gel was synthesized by in-situ hydrolysis method in the present of silane coupling agent. Then dendrimer-like polyamidoamines based on the silica gel surface (PAMAM-SG) were prepared using Micheal addition of the amino and methyl acrylate, and ester-exchange of ethylene diamine and the ester group. The effects of solution pH, concentration and temperature on the adsorption capacity of PAMAM-SG for Cr3+were studied. The optimum pH range is 4.0-7.0. The adsorption rate decreased with increasing the time, but increased with increasing the temperature. The adsorption capacity increased with increase of the concentration until the adsorption reached equilibrium. The adsorption capacity increased with the generations of PAMAM-SG.