Methods for the extraction of DNA from the preputial smegma of cattle infected with Tritrichomonas foetus for the purposes of polymerase chain reaction (PCR) detection are usually time-consuming, relatively insensitive and require hazardous chemicals. In order to solve these problems, we have developed a rapid, sensitive and harmless method to extract quality DNA from preputial smegma spiked with T. foetus. Results indicate that the addition of 5% Chelex-100 resin and 0.05% agar solution to the spiked smegma before the process of DNA extraction by the boiling method can significantly increase the sensitivity of PCR detection. This improved method may be suitable for routine DNA extraction for the diagnosis of cattle and even human trichomoniasis by PCR.