The invention belongs to the field of biological medicines, and discloses a 
drug containing 
arsenic nanoparticles, which comprises 
transition metal, 
arsenic and 
protein, and the 
protein is a carrier and is loaded with the 
transition metal and the 
arsenic. According to the synthesized 
drug containing arsenic nanoparticles, single 
protein serves as a template, the particle size of the synthesized 
drug is smaller than 15 nm, the in-vivo 
circulation time can be prolonged due to the 
small particle size, and uptake of tumor to the drug is increased. The drug containing the arsenic nanoparticles hasan acid-responsive release characteristic, and can release the drug for a 
tumor microenvironment and 
tumor cells in a targeting manner, so that the 
side effect caused by non-specific release of the drug is reduced, the local 
drug concentration of the tumor can be improved, and the tumor killing effect is enhanced. Meanwhile, the drug containing the arsenic nanoparticles is simple in synthesis mode, mild in reaction condition, cheap and easily available in reaction raw materials, low in purification cost and small in environmental 
pollution, does not need to use an 
organic solvent, has clinicalconversion potential, and can be produced in a large-scale expanded manner.