The signal picked up by the vessel's black box detector had a frequency of 37.5kHz per second - identical to the beacon signal emitted by flight recorders.
The announcement came nearly a month after the Malaysian jetliner disappeared off radar screens en route from Kuala Lumpur to Beijing with 239 people on board, triggering an unprecedented international search.
Australian and British vessels are currently involved in a round-the-clock underwater search in the southern Indian Ocean, hoping to pick up a signal from the plane's black box recorder, but the battery powering those emissions is nearing the end of its roughly 30-day life span.
"Suspected pulse signal picked up by Haixun 01 has not been identified yet," the China Maritime Search and Rescue Center said on a verified microblog.
Australian Defence Minister David Johnston said he had not received a report on the signal and warned that it may not be from the plane.
"This is not the first time we have had something that has turned out to be very disappointing," he told ABC television.
"I'm just going to wait for (JACC chief) Angus (Houston) and the team and my team to come forward with something that's positive because this is a very, very difficult task."
The news agency also reported that a Chinese air force plane spotted a number of white floating objects in the search area Saturday.
The plane photographed the objects over a period of 20 minutes after spotting them at 11:05 local time.
An Australian pilot on board the plane reported the information to the Joint Agency Coordination Center (JACC), which is coordinating the massive multinational search in the southern Indian Ocean.
The plane, taking off at 6:04am, was the first to leave Perth International Airport for the day's search schedule. It arrived at the designated area, about 2,700 kilometers from Perth, at 09:55am.
Search conditions were difficult with gales of 4-5 m/sec, waves of 1 to 2 meters and a cloud ceiling of about 200 meters.
The plane returned to the airport at 2.20pm.