The invention provides a video quality of service monitoring method, device and system. Partial video logs satisfying a preset condition are extracted from a video log file, so the occurrence of the problem that a normal operation rate of a video server is reduced can be avoided. Classification calculation is carried out on the video downloading speed of all video logs through utilization of attribute information of the video logs satisfying the preset condition, and a video quality of service result can be rapidly generated in the video server. The problem that the video log processing time is too long due to the fact that distributed processing is carried out on a plurality of collected video logs and then summarization calculation is carried out is solved. The partial video logs satisfying the preset condition are directly extracted for calculation of the video quality of service result, through utilization of the video server, so the video log processing duration and processing operation steps can be effectively reduced on the basis of not influencing the normal operation rate of the video server, and the timeliness of the video quality of service result is further ensured.