Blagg and Gallantree, who finished seventh in the 3m synchro at the London 2012 Olympics last summer, won their third successive British title together last month.
They recorded their highest total as a partnership, 312.24, in Plymouth and, despite not hitting that mark again, they secured silver in the 3m synchro in China.
Blagg and Gallantree scored 305.79 as Chinese duo Tingmao Shi and Minxia Wu won gold in the Water Cube, the Olympic venue during Beijing 2008, with a total of 336.60.
Gallantree, who finished 25th in the 3m individual at Beijing 2008, also competed in the 10m platform with Jenny Cowen on the opening night finishing sixth with a score of 282.60.
Elsewhere Nick Robinson-Baker and Chris Mears, who finished fifth in the men's 3m synchro at London 2012, were the only other Brits in action in the Water Cube also placing sixth with 375.57.