Cross-boundary sharing of government data could help to promote coordinative work of different departments and improve administration efficiency. Using case study as research method, the author examined the cross-boundary data sharing of two representative city governments of China. Nine problems were found existing in the cross-boundary sharing of government data and 5 reasons behind them. Then policy suggestions were put forward from 3 aspects, including building effective data governance system, strengthening institutional supports and improving the government data sharing platform.