Aiming at miniaturization, high resolution and weak-signal detection of portable Raman spectrometer, the rational optical systems of the high-resolution grating spectrometer and the optical probe system with large object space numerical aperture (NA) are designed, and the testing of the performance of the prototype Raman spectrometer is completed. According to the aberration theory of the Czerny-Turner(C-T) grating spectrometer, under the coma-free condition, the relation between the imaging plane and the system parameters of the grating spectrometer is established, which ensures the perfect match between the size of the image plane of the system and the size of the linear-array CCD, and then the design of the new coma-free C-T grating spectrometer is completed. By use of the telephoto optical structure of the “thick doublet”, the compact optical probe system with object NA of 0.33 is designed which perfectly matches with the entrance pupil of the grating spectrometer. The results of the spectral resolution are better than 0.6 nm and the Raman spectrum ranges from 781 nm to 1014 nm, with the prototype size of 243 mm×25 mm×71 mm. The five characteristic peaks of Raman spectrum of CCL4 are successfully measured by the prototype Raman spectrometer, which verifies the feasibility and the rationality of the optical design of the whole Raman spectrometer system.