The official services Purchasing Managers' Index (PMI) released by the National Bureau of Statistics dipped to 54.5 from February's 55.0, but remained well above the 50 level that is the dividing line between expansion and contraction.
"The data shows that China's non-manufacturing industry still maintained a relatively fast growth rate," said Cai Jin, a vice president at the China Federation of Logistics and Purchasing, which compiles the PMI, in a statement accompanying the data.
"The employment situation also continued to become stable and better."
On Tuesday, two surveys showed manufacturing struggled in March, with activity at smaller, private firms contracting for the third month in a row.
On Wednesday, China's cabinet said it would accelerate construction of rail projects and cut taxes for small firms, in what appear to be the first steps it has taken this year to steady the economy.
Services made up 46.1% of gross domestic product in 2013, having overtaken manufacturing as China's biggest employer in 2011. The sector has weathered the global slowdown much better than the factory sector.
A separate PMI survey of the services industry by Markit Economics and HSBC will be released at 0145 GMT on Thursday. That survey covers more smaller, private firms than the official PMI.