Resistance rotary level meter using magnetic motor driven rotating blade. When tested materials rose to the position of the blade, the blade passive obstruction, the resistance through the shaft drive to the junction box detection means for detecting a switching signal output device out and cut off electrical power to make the blades stop turning. On the contrary, the material fall, leaf loss of resistance will be restored to the rotating state. The proportion of materials for different blade rotation sensitivity can be adjusted by adjusting the spring tension. The switch is widely used in ore, fertilizer, cement, coal, grain, feed, plastics and other solid materials up and down inside the silo alarm or control.