The invention provides a solar telescope diaphragm with high cooling efficiency. The solar telescope diaphragm comprises a diaphragm body having a diaphragm light hole in the middle and an annular hollow cavity therein; one end of the diaphragm body facing to incidence of light of a focal point of a telescope is called a reflective surface, and the other end of the diaphragm body is called a bottom surface; a spacer is disposed in the annular hollow cavity of the diaphragm body; one end of the spacer is fixedly connected to the bottom surface of the diaphragm body, and the other end of the spacer is close to the reflective surface of the diaphragm body; one end of the spacer close to the diaphragm body is an annular end face; a gap between the annular end face of the spacer and the reflective surface of the diaphragm body forms a cooling cavity; the position of the annular end face corresponds to an irradiated area on the reflective surface when the center of the sun is observed via the telescopic, the annular end face is similar to the shape of the irradiated area, and the area of the annular end face is not less than that of the irradiated area; and the spacer divides the annularhollow cavity of the diaphragm body into an inner side cavity and an outer side cavity, and the inner side cavity and the outer side cavity communicate with each other through the cooling cavity.