The Chinese mainland's trade with Hong Kong totaled 259.98 billion U.S. dollars in the first ten months of 2015, down 12.1 percent year on year, according the Ministry of Commerce.
This accounts for 8.1 percent of the mainland's total overseas trade in the same period, figures released by the ministry show.
The mainland's exports to Hong Kong hit 251.32 billion U.S. dollars, a decrease of 12.2 percent year on year, while the mainland's imports from the region dropped 10.6 percent to 8.66 billion U.S. dollars.
Hong Kong is the mainland's fourth-largest trade partner and third-largest export market.
The mainland approved 10,396 Hong Kong-invested projects from January to October this year, with the actual use of Hong Kong capital hitting 71.29 billion U.S. dollars, up 10.9 percent from the same period last year.
As of the end of October 2015, 383,463 Hong Kong-invested projects had been approved by mainland authorities.