The invention discloses a raw grain detector and a detection light path system thereof. The detection light path system comprises a recognition device and a sight glass group for carrying out multisurface imaging on raw grain; the sight glass group comprises a plurality of sight glass modules; the sight glass modules are arranged on the same imaginative spherical surface in a spaced manner; a dropping path of the raw grain passes the sphere center of the imaginative spherical surface; each sight glass module faces towards the sphere center and is suitable for the imaging on the surfaces of theraw grain dropping to the sphere center; and the recognition device is connected with the sight glass group so as to receive imaging information of the sight glass group and obtain completeness information of the raw grain through analysis on the imaging information. According to the detection light path system, the multisurface imaging can be carried out on the raw grain and the completeness information can be obtained through analysis, and high precision and rapid detection on the raw grain can be realized.