The video site, a part of the empire that includes Google, has also decided that all videos which figure in its top content, known as Google Preferred, will be reviewed by humans before being allowed to remain there.
The changes were announced overnight in the US by YouTube chief product officer Neal Mohan and chief business officer Robert Kyncl.
Last year, YouTube came under pressure to clean up its act after ads of well-known brands were found to be appearing on videos that contained racist, sexist and anti-Semitic content.
In November, it was reported that clips of scantily dressed children were carrying ads from brands like Mondelez, Lidl and Mars.
Mohan and Kincl said: "Though these changes will affect a significant number of channels, 99% of those affected were making less than US$100 per year in the last year, with 90% earning less than US$2.50 in the last month.
"Any of the channels who no longer meet this threshold will be paid what they’ve already earned based on our AdSense policies. After thoughtful consideration, we believe these are necessary compromises to protect our community."
In April last year, Google set a YouTube Partner Programme requirement of 10,000 views for videos to carry ads. This time, that has been cut further.
Thousands of contractors will review the clips on Google Preferred. Within that section, the company says it will have "a three-tier suitability system" that will “give them appropriate placements for their brand, while understanding potential reach trade-offs", according to the website Recode.