The purchasing managers' index (PMI) for China's nonmanufacturing sector came in at 53.8 in December, up from 53.4 in November, the National Bureau of Statistics (NBS) said Dec 31.
A reading above 50 indicates expansion, while a reading below reflects contraction.
The nonmanufacturing PMI averaged 54.4 in 2018, remaining in general at a relatively high level, said NBS senior statistician Zhao Qinghe.
The service sector, which accounts for more than half of the country's GDP, maintained stable growth, with the sub-index measuring business activity in the industry coming in at 52.3 in December, slightly lower than 52.4 last month.
Rapid expansion was seen in sectors including rail transport, banking, insurance, and telecommunications, where the readings were all above 60, the NBS said.
Monday's data also showed that China's manufacturing PMI stood at 49.4 in December, down from 50 in November.