An estimated 100,000 people now live in the Abu Shouk and As-Salam camps.
At least 200,000 people have died since the rebellion erupted in February 2003, according to United Nations estimates.
Western pressure
Liu's visit comes as the US and other Western nations push for tough sanctions against the Sudanese government, accused of masterminding a counterinsurgency campaign in Darfur.
As one of Sudan's most important trading partners, Beijing has been criticised for not using its influence to press the Sudanese government to end the violence in Darfur.
Some human rights groups have called for a boycott of the 2008 Beijing Olympics unless China takes firmer action.
China buys two-thirds of its oil and is accused of selling the government weapons used in Darfur despite a UN embargo.
Speaking on his visit Liu said China would continue to play a constructive and positive role in seeking a settlement to the conflict.
He said Beijing had offered an additional financial assistance of $80m for Darfur, with two of four instalments already paid.