The Congressmen lodged their strong protest against the BJP for organising the political event "Yuva Udghosh programme" at the sports ground of Mahatma Gandhi Kashi Vidyapeeth.
BJP president Amit Shah is also expected to address nearly 17000 youths at the event.
Prominent among those detained include Congress Legislative party leader Ajay Kumar Lallu, former MP Rajesh Mishra, former MLA Ajay Rai, District unit president Praja Nath Sharma, a media release from the party said.
The detained Congressmen were taken to the Varanasi Central Jail.
Nearly 25 students of Mahatma Gandhi Kashi Vidyapeeth were also detained for allegedly planning to protest against BJP chief Shah and UP Chief Minister Yogi Adityanath, a police officer said.
Increased police vigilance is being maintained in and around the venue to avoid any sort of protest during the programme, the officer added.