More than 5,300 bottles of alcohol were seized by the investigators in the southern city of Liuzhou.
They also found packets of a white powder called Sildenafil, better known as the anti-impotence drug Viagra.
Police in the Guangxi region are now investigating the two distillers.
The Liuzhou Food and Drug Administration said (in Chinese) that the powder was added to three different types of 'baijiu' - a strong, clear spirit that is the most popular drink in China.
They said the haul was worth up to 700,000 yuan (£72,000; $113,000).
Doctors recommend that adults requiring prescription should take only one dose of Viagra a day, with a lower dose for those over the age of 65.
China continues to face widespread food safety problems.
In June, police in cities across China seized more than 100,000 tonnes of smuggled meat, some of which was more than 40 years old.
The 2008 tainted milk scandal outraged the nation.
Some 300,000 people were affected and at least six babies died after consuming milk adulterated with melamine.
