Provided are a non-metallic cylinder for electromagnetic compatibility testing, a rotary angle adjustable antenna device, and a rotary angle adjustable antenna system. The rotary angle adjustable antenna device provided by the present disclosure includes a non-metallic cylinder, a first adapting piece, and an antenna; the antenna is mounted in the first mounting hole with a rotary sleeve arranged outside, at least one end of the antenna extends out of the first mounting hole; the first adapting piece is further provided with a second mounting hole, the first piston rod of the non-metallic cylinder is placed in the empty slot of the first adapting piece after passing through the end cover of the non-metallic cylinder then passing through the second mounting hole of the first adapting piece; the first piston rod of the non-metallic cylinder is connected with the rotary sleeve.