An optical detection system and a laser providing module without using an optical fiber thereof are provided. The optical detection system includes a carrier module, a laser light providing module, and an electrical detection module. The carrier module is configured to carry a plurality of photodiodes. The laser light providing module is disposed above the carrier module. The electrical detection module is adjacent to the carrier module. The laser light providing module is configured to convert a laser light source into a plurality of laser light beams, thereby simultaneously and respectively exciting two corresponding ones of the photodiodes. The electrical detection module is configured to simultaneously and electrically contact the corresponding photodiodes so as to obtain an electrical signal generated by each of the photodiodes.