How to Choose a Royal Bride (1985)

Emperor Kangxi's mother tries to marry him with the daughter of an official, but she's too strong-willed to agree to an arranged marriage even if it is with the Emperor, so she dresses as a man and heads off to Jiang Nan to see the spring blossoms. As luck would have it, Kangxi also decides to head to Jiang Nan in disguise in search of adventure, and the two cross paths and quickly become firm friends.