At present, there is no official data to show which province in China has the most Koreans. The distribution of Koreans will change with time, policies and other factors.
However, based on past statistical data and general observations, we can draw some inferences:
Three northeastern provinces: Due to their close geographical location to the Korean Peninsula and frequent historical and cultural exchanges, the three northeastern provinces have always been one of the main settlements of Koreans in China.
Shandong Province: Shandong Peninsula and the Korean Peninsula face each other across the sea. There have been many exchanges in history, so there are also many Koreans living in Shandong Province.
Beijing, Shanghai, Guangzhou and other first tier cities: as economic centers, these cities have attracted a large number of foreign talents, including Koreans.