Thanks Francois,

How can I map them to Alt-f and Alt-b ?

Write something like the following and save it as a style file in "~/.TeXmacs/styles/mystyle.ts" ?

(kbd-map
  (:profile emacs)
  (:mode in-text?)
  ("alt key f"  .... and how about the cursor movement !? )
)

Thanks!
Hongying
PS: I read the manual on page 73 and some source code, but I'm still not quite sure.

some source from "texmacs/src/TeXmacs/progs/texmacs/keyboard/prefix-kbd.scm"

(kbd-map
  (:profile emacs)
  ("altcmd" "" "Alternate TeXmacs command"))

(kbd-map
  (:profile emacs)
  ("altcmd" "" "Alternate TeXmacs command"))

source from "/texmacs/src/TeXmacs/plugins/mupad/progs/init-mupad.scm"
(kbd-map
  (:mode in-text?)
  ("text" "" "TeXmacs command")
  ("text:symbol" "" "Insert a special character"))

  (kbd-map
    (:mode in-mupad-prog?)
    ("quot;  (insert "quot;))
    ("\"" (insert "\""))
    ("."  (insert "."))
    ;; ("_"  (insert "_"))
    ("`"  (insert "`")))

  (kbd-map
    (:mode in-mupad-math?)
    ("quot;  (insert "quot;))
    ("\"" (insert "\""))
    ("."  (insert "."))
    ("`"  (insert "`"))))