Salmon, 18, joins the club until the end of January 2021.
The striker initially joined Altrincham from Trafford in November 2019 before remaining on loan with the Northern Premier League Division One West Side for the rest of last season, scoring 13 goals in 35 appearances in total.
"I'm thrilled to have signed Lewis, we have been a little disappointing in attack during pre-season so far," said manager Simon Haworth
"We really like what we see in Lewis, he is well thought of at Altrincham and also at Trafford.
"He has got good pace and has a hunger to do well. He can score goals and I am extremely excited to start working with him."
Keep up-to-date with our exclusive email newsletters.
Subscribe