All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is permissible for a woman to perform prayer wearing loose-fitting trousers that do not outline or define the shape of her body. If the trousers are tight-fitting, then it is disliked to perform prayer in them if she is performing the prayer away from non-Mahram men. It is recommended for her to wear a long shirt or the like over the trousers. However, if she is seen by non-Mahram men, then it is impermissible for her to wear trousers or pray in them.
Allaah Knows best.