A man has allegedly grabbed a Taser and fired it at an officer during a tussle with police at a western Sydney train station.

Police had stopped Jason McGoldrick, 50 and a 31-year-old Waterloo woman, at Yennora train station and discovered neither had a valid Opal card.

Jason McGoldrick, 50, has been charged after allegedly tasering a police officer at a train station in Sydney's south-west. Credit:Nine News/Facebook

They also learnt Mr McGoldrick had breached a domestic Apprehended Domestic Violence Order.

A struggle ensued as officers tried to arrest him.