Hi！
  I have trouble taking off manually. Every time when I switch the autopilot on CMD mode, it swiftly pulls the yoke,causing a wide attack angal and a high vspeed, which made the jet stall in a low altitude and eventually crash.
  I've already set a low vspeed(about 100) in the APFDS panel, but it doesn't work. I wonder whether you met such problem and how can I solve it. Thanks.

100 KIAS is a very slow speed to have the L-1011 set to when you need to be at 1000ft AGL, and V2+20, and calling "Flaps 4", followed by being at V2+60 to call "Flaps up". Then you need to be at V2+70 to latch IAS (press the IAS button, which is different to using the AS, and AT to maintain v2+70 (or ~230 IAS)) to 3000ft AGL.

Considering that V2 could be as high, or higher, than 160 KIAS (I don't have any tables to go on, so this is only an estimate, and I tend to use 145 as VR, and around 160 as V2, on an L-1011 at MTOW), so therefore, 160+70 (230) might be the best minimum setting to enter into the AS (although I use 220 for the AS, as it is 10 below maximum speed for Flaps 15 (the takeoff setting)). This the basis of my previous response.