A method of preparing radioisotope hybrid nanocomposite particles using a sol-gel reaction, and radioisotope hybrid nanocomposite particles prepared using the same are provided. The method includes preparing a complex precursor using a metal ion and an unshared electron pair reactive compound, growing hybrid nanocomposite particles based on the complex precursor by means of a sol-gel reaction, calcining the nanocomposite particles in the air to remove organic matters present in the nanocomposite particles, and irradiating the nanocomposite particles with neutrons to prepare radioisotope hybrid nanocomposite particles. The radioisotope nanocomposite particles prepared using the method can be used as diagnostic and therapeutic particles in the fields of oil refining, chemistry, cement, agriculture, water resources, environment, ocean, and medicine, and can also be used as a radioisotope tracer for evaluating the risk of nanomaterials.