Echelle spectrometer is becoming a hot research and focus of modern spectrograph with the outstanding features of high resolution, small size, full spectrum transient direct- reading. In order to further refine its volume, improve the signal to noise ratio and the detection limit, a new structure of echelle spectrometer is designed. By folding main optical path, the new design has smaller size and lower stray light without reducing spectral resolution and image quality. It′ s optical size is less than 165 mm × 70 mm × 65 mm, and spectral resolution is 0.06 nm@200 nm. The baffle and diaphragm is designed to further reduce stray light. Through ray tracing simulation, the stray light of the new echelle spectrometer is less than 2×10-5 , the signal to noise ratio is improved significantly.