You're going to want to vent sex a white Chinese to figure out exactly what it is. If you've ever sexed rabbits then it's the same principle: hold the animal upside down, open the vent and if anything comes out then it's a male. If it's an adult then you'll definitely be able to see the difference between male and female.
Some people swear by the sound of the voice, but I've never been able to accurately tell the difference, even after spending hours outside listening to geese whose genders I already knew.
Good luck. If you need more information about vent sexing let me know. It isn't as daunting as people make it out to be
Vent sexing is best done by experts or at least you should have someone teach you in person. IT is less risky to the goose if it is out of the delicate gosling stage, though finding out a sex is not worth risking a black eye from a well placed wing. LOL