Handheld Raman spectrometer probe system shares the same optical configuration for illumination and light receiving. Thus, stray light caused by multiple reflections of laser, expect for Rayleigh scattering, is a problem to be solved for this kind of probe system. By real ray tracing method, setting up reasonable stray light analysis model and theoretical calculation, we get the total stray light information, together with our actual prototype structural data, such as the size and location of focus, emergent direction, energy in the slit and so on. Then a new approach of stray light suppression for spectrometer probe system that uses black board to block the stray light is proposed. The size and location of the black board are determined according to the analysis of the stray light. The optical simulation analysis results show that the black board suppresses stray light to the level of 10-13 in Raman spectral region. This satisfies the requirements of the handheld Raman spectrometer. With black board method, almost 50% of the laser reflection with incidence angle larger than 2° on the notch filter can be filtered.