Baidu found that in the last quarter of 2015, map query volumes were up 15.4 percent year-on-year, which corresponded with a 14 percent rise in Apple's China revenue in that same period.
But in the first quarter of 2016, map queries declined 24.5 percent year-on-year, which was parallel with a 26 percent decline in Apple's China revenue.
"The impressively strong correlation indicates that map query data provides possibilities for us to 'nowcast' the company's revenues and reveal the future trends. Based on our analysis of latest data, we project that the Apple's revenue in China of second quarter of 2016 may be down around 20 percent on a year-over-year basis," Baidu concluded.
The "second-quarter" that Baidu references is Apple's fiscal third-quarter and will be announced on July 26. Apple did not respond to a request for comment when contacted by CNBC.
Apple has been struggling in China recently and losing market share due toincreased competition from domestic rivalssuch as Huawei, Vivo and Oppo. The U.S. tech giant is expected to face its first down year for iPhone in 2016 with shipments dropping from 232 million in 2015 to 227 million in 2016, according to IDC. In April, China shut down iTunes Movies and iBooks just six months after Apple introduced the services there, adding to the company's woes.
Apple has been trying to make in-roads into China, recently investing $1 billion in Chinese ride hailing app Didi Chuxing.
Baidu is hoping to sell its services, and it also outlined ways in which it could predict other economic metrics about China, given that investors have been quite skeptical about official figures out of the world's second-largest economy.
"These features are quite valuable to market participants and policy makers who need timely and reliable data to make decisions," Baidu said in its research note which it used to introduce "Mobimetrics: it dedicates to quantify the dynamics of social system by analyzing massive individual mobility data."