Sexual offence is one of social problem that often happened in society. One of the best evidence used for investigation was semen and sperm found in a victim's dress. A dress usually made by cotton fabric. This research aimed to discover the influence of washing method to semen and sperm test result in a cotton fabric. This research planned as experimental research, used berberio test for semen and baechi test for sperm test. The result concluded that semen still visible up to 7 days, while the sperm only lasts 3 to 4 days. Conclusion there is no influence of washing found in semen test result while the washing method did influence the sperm test result in the cotton fabric