In nature, most animal species are polygamous, and strict female monandry is rare. Though traumatic mating has been reported to postpone female re-mating, it rarely leads to strict female monandry. We demonstrate that traumatic mating causes strict female monandry in a wandering wolf spider Pardosa pseudoannulata. We showed direct evidence that male damaged the inner walls of the female genital tracts with the sharp embolus on its pedipalps during insemination. To confirm that the trauma reduced female’s willingness to re-mate, we mimicked male pedipalp insertions by micro-injecting seminal fluids and/or causing trauma to female genital tracts and let them mate after the manipulations. Result of mating trials showed that seminal fluids have little impact to restrain female’s mating willingness. However, once female genital tracts were wounded, its mating willingness would be greatly suppressed. In addition, impermeable amorphous mating plugs appeared in female genital tracts after mating. The mating plugs blocked female’s genital tracts and completely prevented female from re-mating. We found that the components of mating plugs shared highly similar organic compounds and concentration percentage of free amino acids with female haemolymph, indicating that wounds caused by male traumatic mating lead to haemorrhages, which gradually turn into mating plugs. We thus provide evidence for strict female monandry being caused by male traumatic mating through two means together: genital trauma suppressed female’s re-mating willingness and haemorrhage from the wounds formed impermeable mating plugs that completely prevented female from re-mating.