Duda, who is running for a second term in a presidential election next weekend, said he wanted to “support Polish families, protect Polish children”.
In his bid for another five years in office, Duda is backed by the ruling conservative Law and Justice party, which champions traditional values.
During his election campaign, conservative politicians have warned that predominantly Catholic Poland is under threat from what they describe as “LGBT ideology”.
Duda announced that he would submit his plan to the lower house of parliament on Monday.
Under Polish law, any alteration of the constitution must be backed by at least two-thirds of deputies in the lower chamber.
Law and Justice and its junior partners in the ruling coalition do not have such a majority, but conservative politicians have voiced hope that some opposition deputies will support the move to prevent gay couples adopting children.