Thanks to the guide and its participants, I successfully installed OS X 10.11.4 on my XPS 15 9550.

OS-X-10-11-4-on-XPS-15-9550

The guide is considerably perfect. Just follow the steps and you’ll get a well-done Hackintosh.

My Clover directory, DSDT & SSDT and Kexts are uploaded to Github, for reference only.

Update: Now I upgrade to 10.11.5, and everything is fine.