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According to Visa policy of Antigua and Barbuda - Wikipedia
Permanent residents of the United States and Canada and holders of valid visas of the United States, Canada, Schengen Area and the United Kingdom do not require a visa.
And to Timatic
Visa Exemptions:
A max. stay of 30 days for holders of a valid visa issued by Canada or USA and if paying a USD 100.- Visa Waiver fee on arrival.
The Chinese citizen doesn't require to apply for a separate visa (he can use his USA visa) but it is necessary to pay 100 $ Visa Waiver fee when he will arrive to Antigua and Barbuda.