The invention belongs to a sonar technology and particularly relates to an unpowered sonar unfolding and folding device which is applied to sonar operation of a helicopter and a ship. The unpowered sonar unfolding and folding device disclosed by the invention comprises a balanced cylinder, a push rod, a positioning assembly, a piston and a safety spring, wherein the piston is arranged in the balanced cylinder; the balanced cylinder is arranged in a sonar shell; one end of the push rod is connected with the piston and the other end of the piston passes through the balanced cylinder to be hinged to a sonar antenna; one end of the safety spring is connected with the push rod and the other end of the safety spring is connected with the inner wall of the sonar shell; the positioning assembly is an elastic part, is arranged on the side wall of the sonar shell and passes through a balanced cylinder positioning hole to be in squeezed contact with the wall of the piston. According to the unpowered sonar unfolding and folding device, all acting forces are balanced by the balanced cylinder, so that the device can implement unpowered sonar unfolding and folding, the sonar detection range and accuracy are effectively improved and the unpowered sonar unfolding and folding device has high practical application value.