It happened at the Ho Choi Grocery store on the 2300 block of South 9th Street.
Police say the two suspects walked into the store at 11:30 a m., made a purchase and left.
The pair then returned at 7:45 p.m.
One suspect immediately went behind the counter and grabbed the 25 year-old clerk by the neck, forcing her to the ground and covering her mouth.
The second robber jumped over the counter and stole lottery tickets, cigarettes and cash from the register.
They both fled the store and were last seen running east on Wolf Street.
The clerk was not injured during the robbery.
Police describe the first suspect as a black male, 6'0" tall. He was wearing a dark colored hooded sweatshirt, black mask, dark colored hat,blue jeans, and gloves.
The second suspect is described as a black male, 5'8" tall. He was wearing a grey hooded sweatshirt, black mask, blue jeans, and gloves.
If you see either of these men do not approach them and call 911 immediately.
Anyone with information on this robbery should call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).
All tips will remain confidential.