Due to the controlled release of Ag+, silver nanoparticles (AgNPs) not only display excellent anticancer activity but also possess cytotoxicity on normal cells. Up to now, no efficient method has been found to eliminate the side effect. In this study, AgNPs with different morphologies were synthesized and some main factors, i.e., the seed amount, CTAB concentration and temperature were discussed. Histidine (His) was applied to modify three kinds of AgNPs (near nanospheres, short nanorods and long nanorods) prepared by the above controlled synthesis, and the bioactivity of the modified AgNPs on cancer and normal cells was investigated. The results showed that the morphology and particle size of AgNPs had strong dependency on the quantity of seeds and reaction temperature except for CTAB concentration. IR spectra showed that His molecules had linked to AgNPs by coordination between AgNPs and C-N group of the imidazolyl in His. The bioactivity experiments in vitro showed that the cytotoxicity of His-modified AgNPs on HL7702 cells was effectively reduced and the anti-tumor activity against MCF-7 cells was not influenced obviously. The results supported that the His-modified AgNPs possess less cytotoxicity and higher targeting anticancer activity and thus the silver nanomaterials modified by His displayed potential applications for cancer therapies. We also suggested that the possible mechanism on the reduction of the cytotoxicity was that His-modified AgNPs could target cancer cells to decrease the cytotoxicity but affect a little on the viability of normal cells.