The blazed grating with the Rowland structure has the advantage of self-focusing and is chosen as the major component in the spectrometer chip. In simulations for the blaze angle design in visible spectrum, we discover the phenomenon of the double reflection diffraction. Its cause and parameter space are discussed. The spectrometer utilizing the phenomenon has similar performance to the grating with the ordinary diffraction and is easier to manufacture in microelectromechanical systems (MEMS) technology. The discovery will greatly ease the design of the spectrometer chip.