Hello
I have one p2p link of 1km good line of sight
configures 5Ghz N, 20/40 Mhz HT Above, TCQ=94%
Signal level 65/63 with speed approx 135 mbps/65mbps


but ping response is not very stable, when we ping any network device sometimes it gives 1000ms ping response for few minutes.


what could be the issue and how can be resolved

What protocol are you using ?
Also it seems strange that on this distance and this signal your rates are not 150/150 (or even 300/300 if mimo) all the time. You have some problem.
No information on the equipment used.

Hello
I have one p2p link of 1km good line of sight
configures 5Ghz N, 20/40 Mhz HT Above, TCQ=94%
Signal level 65/63 with speed approx 135 mbps/65mbps