Abstract: A highly active arithmetic coder of the adaptive binary arithmetic entropy coding algorithm(CABCA) is given out, which is based on context. CABAC is the entropy coding method adopted in the new H.264/AVC. As the development of ultra high definition video, a more harsher requiment of arithmetic encoder is proposed in compression. However, the CABAC is very complex so that it is very hard to be implemented by hardware. To meet the requiment, a high-speed arithmetic encoder structure is proposed according to double-path context storage and pipeline design,which can eliminate the data dependence and get high throughput with very little cost.