We apply differential affine velocity estimator (DAVE) to the Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) 12-min line-of-sight magnetograms, and separately cal- culate the injected magnetic helicity for the leading and the following polarities of nine emerging bipolar active regions (ARs). Comparing magnetic helicity ux of the leading polarity with the following polarity, we nd that six ARs studied in this paper have the following polarity that injected more magnetic helicity ux than that of the leading polarity. We also measure the mean area of each polarity in all the nine ARs, and nd that the compact polarity tend to possess more magnetic helicity ux than the fragmented one. Our results conrm the previous studies on asymmetry of magnetic helicity that emerging bipolar ARs have a polarity preference in injecting magnetic helicity. Based on the changes of unsigned magnetic ux, we divide the emergence process into two evolutionary stages: (1) an increasing stage before the peak ux and (2) a constant or decreasing stage after the peak ux. Obvious changes on magnetic helicity ux can be seen during transition from one stage to another. Seven ARs have one or both polarity that changed the sign of magnetic helicity ux. Additionally, the prevailing polarity of the two ARs, which injects more magnetic helicity, changes form the following polarity to the leading one.

Abstract
1. INTRODUCTION
2. METHOD AND OBSERVATIONS
3. RESULTS
    3.1. AR 11072 and AR 11076
    3.2. The Other Seven ARs
4. DISCUSSION AND SUMMARY
REFERENCES

• DAN YANG(Yunnan Observatories, Chinese Academy of Sciences, University of Chinese Academy of Sciences) CORRESPONDING AUTHOR
• YUNCHUN JIANG(Yunnan Observatories, Chinese Academy of Sciences)
• JIAYAN YANG(Yunnan Observatories, Chinese Academy of Sciences)
• YI BI(Yunnan Observatories, Chinese Academy of Sciences)
• BO YANG(Yunnan Observatories, Chinese Academy of Sciences, University of Chinese Academy of Sciences)