Abstract: A quick release structure of a diaphragm assembly of a stethoscope is disclosed, including a stethoscope having two collecting surfaces each being connectable with a diaphragm assembly. The collecting surface has a portion adjacent to an outer periphery thereof and formed with an annular fitting groove that has a height lower than the collecting surface. The collecting surface is formed with a trough. The annular fitting groove has an inclined internal wall. The diaphragm assembly includes an elastic piece combined with a diaphragm assembly. The elastic piece includes a raised rib, a projection portion, and an inclined inside surface. Through pressing the raised rib into the annular fitting groove, the inside surface is set in tight engagement with the internal wall, and this, in combination with the projection portion fit in the trough, forms a secure and stable fitting engagement and allowing easy release performed in an opposite way.