Highly stable amorphous calcium phosphate (ACP) porous nanospheres with a relatively uniform size and an average pore diameter of about 10 nm have been synthesized by using a microwave-assisted hydrothermal method with adenosine 5′-triphosphate disodium salt (ATP) as the phosphorus source and stabilizer. The as-prepared ACP porous nanospheres have a high stability in the phosphate buffer saline (PBS) solution for more than 150 h without phase transformation to hydroxyapatite, and the morphology and size were essentially not changed. The important role of ATP and effects of experimental conditions on the formation of ACP porous nanospheres were also investigated. The ACP porous nanospheres were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This method is facile, rapid, surfactant-free and environmentally friendly. The as-prepared ACP porous nanospheres are efficient for anticancer drug (docetaxel) loading and release. The ACP porous nanosphere drug-delivery system with docetaxel shows a high ability to damage tumor cells, thus, is promising for the application in anticancer treatment.