The prosecutor general announced this week that the journalist, Ali Anouzla, has been charged under Morocco's anti-terrorism law with assisting and advocating terrorism.
The protesters in the capital, Rabat, alleged he has been jailed for his independent views and criticism of authorities.
Anouzla, editor of the Lakome website, published a story about and posted the video by al-Qaida's north African affiliate.
The video, released earlier this month, was a rare attack on Morocco and accused the king of corruption.
Amnesty International said Anouzla's jailing "sends the message that any discussion of terrorism ... will be treated by the government of Morocco as a criminal offense."
If found guilty, Anouzla faces a maximum sentence of six years in prison.