Under the change, some red card offences will see a player sent to the sin bin for 20 minutes with the offender then able to be replaced on the field by a teammate off the bench when the punishment has been completed.
Referees can still hand out permanent red cards to reduce a team by a player for the remainder of the contest for offences deemed deliberate and with a high level of danger.
First introduced in southern hemisphere competition, 20-minute red cards will feature in the men's, women's and Under-20s Six Nations.
Last October, the proposed trial of the 20-minute red card in elite levels of the game drew criticism from French rugby chiefs saying it could encourage more aggressive play and expose players to greater risk of injury.
Julie Paterson, Chief of Rugby at Six Nations Rugby, said the law change and other trials were among measures aimed at clarifying areas of the game for players and coaches as well as enhancing the experience for fans.
"The Autumn Nations Series was a great case study for the progress that is being made, and it is going to be incredibly exciting to see this continue and evolve through the Six Nations Championships," she said in a media release on Wednesday.
Among other measures, referees will be going 'on mic' to explain key decisions and 'touch finder' technology will be introduced to support the decisions of the match official, organisers added.
