I have two threads.

Thread1: mov [val1],10 ;this value dynamically changing

Thread2: mov eax,[val1]

My program crash. And i get error: Read\write

How fix this problem ?

I found this:
So, for reading I prefare to use CMPXCHG instruction with LOCK prefix, like:

LOCK CMPXCHG EAX, [J]
For writting:

MOV [J], EAX
SFENSE

fasm 1.73 error cmpxchg rax, [val1]

work fine

lock XCHG rax,[val1]

If you have val1 aligned to a dword boundary then you can read and write the value from any thread without needing any locks. You will always get a fully written value, never any half written value.

If your program still crashes and val1 is aligned then I suspect your problem is with something else.