Heilongjiang is part of Beidahuang Group, China's largest agricultural company and the agreement was signed during a visit by its executives to EuroChem's Usolskiy potash plant in Russia.
The finer details of the agreement were not given, with EuroChem saying the specific terms would be agreed by the parties.
Eurochem CEO Dmitry Strashnov said the MoU "underscores EuroChem's commitment to China and highlights our determination to become a strategic supplier to one of the world's most important agricultural markets".
Test production at Usolskiy started in early 2018, while EuroChem is also developing the greenfield VolgaKaliy project in the same country.
The company previously signed a take-or-pay agreement for up to 100% of the expected future sulphate of potash output from the Colluli potash project in Eritrea, a joint venture between Danakali and the Eritrean National Mining Corporation.