If you want to go to Chengdu East, there is a direct bus to Haikou.
There are 1 train from Chengdu East to Haikou:
K488 Chengdu East Haikou 18:06 and arrived in Haikou at 06:30 the next morning. The whole journey takes 36:24 hours.
Soft sleeper upper berth 770 yuan
Hard berth upper berth 487 yuan
Hard seat 283 yuan