So Yes, you have to upload it again ...
anishgupta wrote:I programmed the esp chip using arduino IDE. Now the AT command is not working. Do i have to reflash the firmware for it to work?
If you want the AT command firmware back, https://www.allaboutcircuits.com/projects/flashing-the-ESP-01-firmware-to-SDK-v2.0.0-is-easier-now/