The unknown man was caught on surveillance camera after he entered the Shell gas station on Oct. 1 at 6451 North Freeway.
Investigators said the man posed as a customer before launching his attack behind the counter.
Video shows the man hitting the woman in the face several times before grabbing the cash drawer.
As the robber tried to flee, the clerk attempted to stop him from leaving the store. He turned and punched her several times again, knocking the woman to the floor.
The suspect is described as a Hispanic man with black hair, standing around 5'7" with a heavy build, between 230 and 250 lbs.
He wore a camo hoodie, tan khaki shorts and black shoes during his assault on the clerk.
You may be eligible for a $5,000 reward for information leading to his arrest.
If you know who this man is or have seen him, call Crime Stoppers at 713-222-TIPS. You can also make an anonymous tip online at www.Crime-Stoppers.org.