The commerce ministry announced the self-initiated probe on Sunday, just weeks after President Donald Trump's administration slapped its latest batch of tariffs on Chinese goods.
The ministry did not immediately announce any new tariffs on the grain, though, and the results of the dumping investigation are not expected until next February.
China is the US's largest buyer of crops like sorghum and soybeans, and tariffs on their import would hurt American farmers.
The US shipped China 4.8 million tonnes of sorghum last year, valued at almost $1 billion, according to China's customs data. That was a sliver of the $14 billion in US soybean imports.
Some analysts have predicted China may aim new tariffs at the Republican-leaning states that make up Trump's base.
Kansas went heavily for Trump in 2016 and was by far the US's largest sorghum producer last year. The state's vast sorghum crop was followed in size by Texas, Colorado and Oklahoma.
"Since 2013, the US's sorghum exports to China have substantially increased and the price has fallen, harming China's sorghum industry," Wang said.
The ministry said the US has exported more than 50 percent of its sorghum crop since 2013.
China's move to self-initiate a dumping investigation rather than by request from industry comes after the Trump administration launched its own self-initiated trade case against Chinese aluminum sheet imports last year, the first such case by the US in over a quarter century.
China said it did not need to receive a request to investigate dumping in "special circumstances" with ample evidence.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)