My configuration:

Transmiter: Spektrum DX 3S
Reciver: OrangeRx GR300 Spektrum DSM2 3Ch 2.4Ghz Ground Receiver
ESC: HobbyKing Brushless Car ESC 60A w/ Reverse
Motor: HobbyKing X-Car 8.5 Turn Sensored Brushless Motor

I have a problem if I accidentally turn off Tx, car suddenly accelerated.
I have to manually turn off ESC to stop motor. Is there a solution for this, is the problem to Tx, Rx or ESC.

If you use the Spektrum SR300 receiver, then it will failsafe to the throttle and steering positions present during the binding process. I'd guess that all of the Spektrum receivers do this. (My SR3500 also behaves this way.)

Or you can just make do with what you have. The behavior you describe was normal on the non-computer radios we had many years ago. You just learn to make sure that the transmitter is on whenever the receiver is on.

Rebind the radio system with the throttle at neutral. Wherever the radio is when binding is where the failsafe is set.

I solve the problem when I rebind the Rx, Thank you all.

Glad you got it sorted but you should practice powering the vehicle off before the radio. And powering the radio on before the vehicle.