"The impact on Lebanon has been tremendous and it continues to have a negative effect on the country's economic, political and social well-being," Xinhua quoted Amos as saying in a statement.
"We must do more to support the people and government of Lebanon as they are struggling to meet increasing demand for services like health, education, electricity, and water and sanitation. We should not take their generosity for granted," she added.
As the Syrian war enters its fourth year, its neighbour Lebanon has received more than one million Syrian refugees, about half of them children.
Amos who arrived in Lebanon on Wednesday visited Syrian refugees in Lebanon's northern Wadi Khaled region and in Minieh district near Tripoli.
"I spoke to children whose parents cannot afford to pay for them to go to school. It is such a waste. An entire generation is at risk," she said after she visited the camps.
Amos also met with Lebanese President Michel Sleiman, Prime Minister Tammam Salam and Foreign Minister Gebran Bassil to discuss how the international community can help Lebanon.