An isp has a block of 1024 addresses.it needs to be divide the addresses to 1024 customers does it need subnetting?

No.

If you have one IP per customer, you don't need to create smaller subnets.

(You won't have enough addresses though - the first and last addresses of the block will be the network and broadcast addresses and won't be useable. You'll only have 1022 usable addresses)