The best-performing Chinese Internet stocks traded in the United States are set to extend their rallies in 2015, unfettered by forecasts for slower growth in the world's second-largest economy.

Vipshop Holdings Ltd, an online retailer whose shares have surged 30-fold since its US debut in March 2012, and car-listing website Bitauto Holdings Ltd may both advance an additional 32 percent in the next 12 months, according to average analyst estimates compiled by Bloomberg. The companies, which doubled this year, have the best performances on the Bloomberg China-US Equity Index since 2012.

While a slowdown in China's economy may cut sales growth, Web-based companies such as Vipshop and Bitauto will retain their competitive advantages by maintaining good relations with vendors, capturing popular niches and expanding services, according to Henry Guo at JG Capital. Of 25 analysts covering Vipshop, 20 rate it a buy and just one recommends selling. None of the nine analysts covering Bitauto has a sell.