The utility model belongs to the technical field of electric power systems, and specifically relates to an optical cable trench on-line inspection instrument. The optical cable trench on-line inspection instrument is characterized by comprising a triangle support frame, a universal shaft coupling and a camera. The bottom of the camera is connected with the upper end of the triangle support frame through the universal shaft coupling. The camera is provided with a power supply which supplies power for the camera. The camera is provided with a wireless transmission module, and transmits acquired images in a wireless manner to tablet computers, mobile phones, laptop computers or desktop computers. According to the utility model, the optical cable trench on-line inspection instrument is capable of acquiring images of optical cable trench construction sites in real time and transmitting the images by wireless transmission technology; besides, the instrument is simple in structure and convenient to carry, and the camera can be freely rotated.