Unfortunately, we don’t have the ” longest” word in China, because all our characters are individual.
However, we have the most complex word.
This one is “Biang”. It is the name of a kind of noodle.
And we still have this one, called “da”. That means a lot of dragons fly together.
BTW, I am not a English speaker. So my English may have some problem, but I am improving. If you have any problem about my answer, please let me know.
I hope this can help you.