The invention discloses a blast furnace burden granularity video detection device and a blast furnace burden granularity video detection method. The blast furnace burden granularity video detection device comprises an imaging device, an illuminating device, a protection sleeve, an on-site control box, a video image processing and display device, an indoor control box, a purification power supply, a sound and light alarm device and a signal converter, wherein the imaging device and the illuminating device are arranged above a conveying belt machine of a blast furnace feeding system, and the signal converter is arranged between the video image processing and display device and the sound and light alarm device. After the structure is adopted, the imaging device is utilized for carrying out image collection on furnace burden on the conveying belt machine, then, the video image processing and display device is used for analyzing and processing video data, the furnace burden granularity size and the distribution condition are calculated, and blast furnace operators can fast and accurately obtain relative information of the furnace burden granularity. The device has the characteristics of accuracy, high speed and efficiency, the existing outdated detection process can be replaced, and important effects of guiding the blast furnace operation and improving the process control level are realized.