In a motion, he proposed that those convicted of serious crimes should be able to be sentenced to death.
Citing criminal cases where the death penalty could have been enforced, Uppsala Nya Tiding newspaper writes that Larsson makes reference to Stig Bergling, the former Swedish police officer who spied for the Soviet Union in the 1970s.
He also mentions Anders Eklund, the man convicted of murdering 10-year-old Engla Höglund in Dalarna in 2008, who is now serving a life sentence.
Board members have already proposed to reject the motion but undeterred by the move, Larsson claims many within the party are in favour of capital punishment.
The Sweden Democrats previously backed the death penalty for certain murder cases and treason, but removed the proposal from their manifesto in 1998.
The party congress – Landsdagarna – is taking place in Skåne, southern Sweden, from 16th-18th October.