Can i take the ferry bewteen shekou port and hong kong airport if i don't have a airline ticket?

No, you need to show the valid intraday airline ticket and then you are allowed to take the ferry because it is a enclosed route.
For reference, you can travel by land. You can pass the border from Luohu Port and enter HK first. Then take East Rail Line to Sheung Shui Station. Then transfer to shuttle bus no.A43 to arrive at HKIA directly. The whole trip takes around 80 minutes. It costs 54.3 HKD per person.

Thanks a lot!! :)