The holidaymakers were spotted by officers on a routine patrol on Saturday snapping smartphone pictures of each other posing with the banned gesture outside the historic landmark in the heart of the German capital.
"A probe on suspicion of using the symbols of anti-constitutional organisations was opened against the two Chinese men, aged 36 and 49," the spokeswoman told AFP.
The pair were questioned at a local police station and released after paying €500 ($589) bail each.
Using the symbols of anti-constitutional organisations, a charge frequently levelled against members of far-right groups, can carry a sentence of up to three years in jail sentence or a fine.
The spokeswoman said the men could leave the country during the investigation and that if a fine is handed down, the bail money they had already paid would likely cover it.
The Reichstag housed the assemblies of the German Empire, the inter-war Weimar Republic and Nazi Germany until it was destroyed by a suspicious fire in 1933.
In the wake of the blaze, Adolf Hitler consolidated his power over Germany, eventually unleashing World War II, which claimed an estimated 20 million lives in Europe, and the Holocaust, in which millions of victims including six million Jews were systematically slaughtered.
Refurbished after Germany's 1990 reunification by British architect Norman Foster, who added an iconic glass dome to symbolize open democracy, it has since 1999 housed the lower house of parliament, the Bundestag.