I am new to UML, regrading FSM diagram, how to represent two transitions that lead to same state, for example, I'm in state1:
when(event1)-->action1-->state2
when(event2)-->action2-->state2
I mean do I need to draw two lines from state1 to state2?
Yes, you have to draw two lines since the event and action is part of the line.
as you can see in http://en.wikipedia.org/wiki/File:UML_state_machine_Fig1.png
your line will get a text like "event1 / action1" and "event2 / action2".
If you don't generate code from your diagram, you can also use one line and add a text like "event1 / action1 OR event2 / action2" if this is more readable.
I consider UML as a guide - sometimes you have to change the rules a little bit in order to create something readable and useful. :-)
