Aldehyde hyaluronic acid-cisplatin (A-HA-CDDP) complex nanoparticles were readily prepared, and CDDP was stably loaded into the core of the NPs through imine bond and coordinate bond linkages. The results show that the NPs were prepared successfully by a chemical complexation reaction rather than by physical mixing. Compared to many CDDP and HA complex nanoparticles evaluated in other studies, A-HA-CDDP NPs with imine and coordinate bonds between the A-HA and CDDP displayed better sustained release behavior and pH sensitivity. Therefore, the acidic tumor environment could accelerate the release of CDDP from the NPs. MTT and AO/EB staining assays showed that A-HA-CDDP NPs had comparable cell inhibition with CDDP in HeLa cells as well as little toxicity to NIH3T3 cells. This result indicates that the chemical reaction between A-HA and CDDP had little effect on the antitumor activity of CDDP and that the NPs actively targeted CD44-rich tumor cells. Both a hemolysis test and a protein adsorption assay demonstrated that A-HA-CDDP NPs had good biocompatibility and blood circulation in vivo. Therefore, the NPs have the potential to be used for targeted CDDP delivery in vivo. A subsequent publication will describe the circulation, targeting and tumor inhibition experiments of these NPs in vivo.