The fair, which opened on Tuesday in Älvsjö outside Stockholm, expects around 1,000 visitors from around the world. On Facebook, a group called "Stop the death fair" said it was planning a "die-in" with volunteers laid out on the ground as if they were dead.
The fair, Future Defence and Security Nordic, is expected to run annually. It is not open to the public, although anyone can apply to attend.
The Swedish Peace and Arbitration Society slammed the organiser, a company owned by the city of Stockholm and the Swedish Chamber of Commerce, for supporting a conference that aims to increase arms trading.
"We think the city of Stockholm and the fair are contradicting their own ethical guidelines about social responsibility when they let companies exporting munitions to dictatorships exhibit and gain access to new business opportunities," says Anna Ek, chair of the Peace and Arbitration Society.
Erik Hasselström, a project manager at FDS Nordic, tells SVT he sees no problem with people voicing their opinions about the fair taking place.
"We have no problem with the criticism that has been putforward by the Society for Peace and Arbitration. We are completely open to those types of organisations coming down in this typ of activity. But we will not respond," Hasselström says.