China's monthly trade surplus dropped to $20.2 billion in May, down 10 percent from the same month last year, the General Administration of Customs said on Wednesday.

Exports in May rose 28.1 percent year on year to $120.49 billion, while imports rose 40 percent to $100.29 billion.

The export growth rate was 0.6 percentage points lower than May last year, whereas the import growth rate was 20.9 percentage points higher.

The total trade volume in the first five months stood at $1,012.08 billion, a year-on-year rise of 26.2 percent.

A Customs analysis showed the acceleration of the yuan appreciation was one of the most significant factors in helping narrow the trade gap.

"The continued strengthening of the yuan helped cut exports by dampening the cost advantage of Chinese products while boosting imports. Many domestic export-oriented companies expanded their import business," the report said.

Trade with the EU, China's largest trade partner, rose 27.9 percent to $166.02 billion in the first five months this year.

The United States secured its place as the second largest trade partner with China, with a total trade volume of $130.47 billion, up 13.3 percent. Trade with Japan came to $106.56 billion.

Trade with India, the eighth largest trade partner, saw the fastest growth among China's top ten trade partners to reach $24.16 billion, up 70.3 percent.