With the development of Internet, the web data has present the characteristics of heterogeneous, text tagging and imbalanced data, which leads to the failure of the traditional online event detection method based on long text. In this paper, we adopt the improved Single Pass Algorithm to detect online heterogeneous media web events. On one hand, we redesign the similarity calculation formula based on the imbalanced data. On the other hand, we design the slice-windows to improve single pass algorithm runtime. The result on SED2014 dataset shows the effectiveness and practicality of our algorithm.