China Unicom, which operates the mainland's second-largest wireless network, says it has received more than 100,000 online reservations for Apple's new iPhone 5C and 5S since the devices were unveiled last week.
The firm has not disclosed pricing plans for the handsets, which will go on sale on Friday.
Apple unveiled the new models for Unicom and China Telecom's networks last week.
It is trying to halt a decline in its share of the world's largest mobile-phone market but that goal may be challenged by reduced support from carriers looking to rein in costs, with China Telecom announcing subsidies on the 5C and 5S that analysts say are about 15 per cent less than those for the earlier model.
"The plan is more conservative this time," said Eva Yip, at Sun Hung Kai Financial. "The handset subsidy as a percentage of upfront payment is less than that of the iPhone 5 plan."
Yip said a China Telecom monthly plan costing 289 yuan (HK$366) for the 5S carried a subsidy of 2,890 yuan, 15 per cent less than the 3,400 yuan for the iPhone 5 on the same plan.
China Telecom declined to comment on Yip's estimates.
China Telecom requires a down payment of 4,488 yuan for any plan with a 16-gigabyte 5C, and 5,288 yuan for the 5S. The handset is free for a two-year contract with a minimum monthly plan of 329 yuan for the 5C or 389 yuan for the 5S.
Unicom might follow a less aggressive approach to subsidies, Cynthia Meng, an analyst with Jefferies, wrote in a report.
"China Unicom and China Telecom are more rational on price competition," Meng wrote, with both "balancing between quantity and quality of new 3G subscriber development".
China Mobile, the mainland's largest phone company, does not have a distribution agreement with Apple for the iPhone.
In Hong Kong yesterday, Apple fans woke up early before online reservation of iPhone 5s started at 6am. Some said they had difficulty loading the webpage.
Gold and white phones were popular among those who were able to reserve their phones. By 7am, only the black ones were available, which were all taken up by 8am, according to posts on discussion forums.
Some internet users said Apple could have limited supply to make the new phones seem like a big hit.
Additional reporting by Amy Nip