Online citizen journalism has been seen developing fast and with popularity with more advanced media platforms in recent years, yet what factors affect citizen journalists’ likelihood to produce public news remain murky. The effect of social capital on health, on politics, on internet, on educational achievement and many other aspects has been studied for diverse groups. This study sought to measure U.S. and Chinese citizen journalists’ social capital and their perceived ability to report public news as well as the influence of social capital on citizen journalists and compare how social capital worked for citizen journalists in the two countries. Social capital, longevity in community, strength of personal relationships, relying on personal social connections as news sources, professional media experience and social media use were measured and analyzed to address the hypothesis and answer research questions. Results showed that U.S. citizen journalists, who were proposed to have higher political openness in their society, perceived a higher level of likelihood that they will have the ability to report public news than Chinese citizen journalists. Longevity in community, professional media experience and level of social capital were all found to positively affect citizen journalists’ perceived ability to report public news and their level of social capital. Citizen journalists with stronger personal relationships were found to have higher level of social capital. Substantial differences of effects from independent variables on dependent variables were found between U.S. and Chinese citizen journalists.