If you have a party of 3 or 4 people, you may consider to hire a taxi for RMB400.00. This would take you to Huanglong Park and back to Jiuzhagou. You would have more flexibility for your Huanglong trip.

Bus Service from Jiuzhaigou to Huanglong

1. JiuTong Bus Services(九通客运服务站 JiuTong Ka Yun) next
to JiuTong Sunshine Hotel(九寨沟九通阳光大酒店).
2. Bus fare to Huang Long RMB48.00(45 bus fare + 3
insurance)
3. You may get the return ticket from the bus driver,
RMB45.00. The bus usually stays at the Huang Long Park
for 4hrs which would allow you sufficient time to tour
the whole park.