The invention relates to a group trajectory accompanying mode online analysis method and system in a big data environment. The method comprises the following steps: setting a threshold parameter of agroup trajectory accompanying mode; slicing the group trajectory flow data to obtain a group position information set of the current time slice; constructing a distributed high-dimensional index treeKD-Tree based on the spark; performing density clustering of the position points to form a group position clustering snapshot cluster set Scs of the current time slice; adding the position clusteringsnapshot cluster in the Scs into an accompanying candidate group existing in the SetAc or a newly generated track accompanying candidate group according to whether the current group track accompanyingcandidate set SetAc is empty or not; and judging whether each current trajectory accompanying candidate group is qualified or not, and outputting qualified group trajectory accompanying mode detailsif the current trajectory accompanying candidate group is qualified. The method has the advantages of high throughput, high real-time performance, high accuracy, good expansibility, high configurability and the like.