"What's the meaning of this sentence? " It's not good to do something or doing something" is a better way of writing your question

It's the same as "it's no use to do..." So the action is pointless or futile. You could also understand it as "no good will come from doing (sth)". Between the two examples, using "doing" focuses on the action of doing itself, while "to do" puts more focus on the 'something' (ie. you could do something else). But really, the meaning is very very close anyway.

i am confused.maybe .not useful. i don't know. looking forward to get the ture answer.