Kerry's tour of Asia begins this weekend and includes stops in China, Japan and South Korea.
The April 10 letter said the Obama administration "has a...solemn obligation to raise concerns about ongoing and severe human rights abuses in China."
It added, "Your visit will set the tone for the U.S.-China relationship in the new Obama term, and is thus a crucial moment to signal to the Chinese government that the quality of its relationship will depend in part on whether it lives by universally accepted human rights norms in its domestic and foreign policies."
The letter listed the many areas where China's human rights record has deteriorated -- including persecution of domestic critics and suppression of religious believers, including Christians -- and noted that "the U.S. response has not elicited meaningful improvement in these areas."
The authors of the letter also pointed out that "as much as the Chinese government appears to resist outside pressure to improve its record, experience suggests that it does respond to such pressure" and added "we urge you to be mindful of the converse: that the Chinese government and people take careful note when the United States is silent."
ChinaAid joined Amnesty International, Freedom House, Human Rights in China, International Campaign for Tibet Reporters Without Borders, Uyghur American Association and World Uyghur Congress in signing the two-page letter.