DNA in the liver, kidney, testes, etc. was amplified with semi-random polymerase chain reaction (PCR) in Wistar male rats exposed to ethylene oxide (EtO) for various times and in control rats with hemoglobin gene-specific primer to study the damage effects of EtO on DNA molecule. Results showed that inhalation of 800 mg/m3 of EtO for six to nine weeks could cause damage to DNA in the liver, kidney and testes, etc. to various extent, with the most serious damage to DNA in the testes.