The Caixin/Markit Services Purchasing Managers' Index (PMI) for China declined to 51.2 in May from 51.8 in April, missing expectations for a rise to 52.0.
The decline was mainly driven by a slower growth in new business and job creation.
"All of the index categories, with the exception of output prices, which remained stable, showed signs of deterioration," Dr. Zhengsheng Zhong, Director of Macroeconomic Analysis at CEBM Group said.