The invention is applied to the technical field of video monitoring, and provides a processing method and a system for monitoring data. The monitoring data is video bitstreams based on H264 coding. The method comprises the steps of obtaining video bitstreams, adding reference frames in the video bitstreams sequentially into reference frame arrays and writing the reference frames into a reference frame storage block; according to the sequence of the reference frames in the reference frame arrays, non-reference-frame arrays corresponding to the reference frames are sequentially added into the non-reference-frame arrays and written into a non-reference-frame storage block; the non-reference-frame arrays, of which a retention period exceeds a preset time threshold value, are released; and if all the non-reference-frame arrays, of which the retention period exceeds the preset time threshold value, are released, the reference frames, of which the retention period exceeds the preset time threshold value, will be released. According to the invention, storage is respectively carried out on the reference frames and the non-reference-frames so as to save storage space; and users are enabled to check monitoring videos, of which the retention period exceeds the preset time threshold value, through the reserved reference frames.