Carol-Anne Norman and her sister set up a camera in their father's home to monitor the care he was being given.
She claims care workers neglected and humiliated her 85-year-old father, who has dementia.
The CPS said there was insufficient evidence to prove any criminal offence had been committed.
Mrs Norman set up the cameras almost a year ago after she suspected her father's medication was being delayed.
One of the incidents it captured showed her father wandering the landing with his trousers and incontinence pad around his knees.
After she showed the tapes to the police, several care workers were interviewed.
The CPS said in a statement that after reviewing the evidence, there was insufficient evidence to prove any criminal offence had been committed.
"While the behaviour might be considered an unacceptable way to treat vulnerable people, it did not cross the line into criminal activity," the spokesman said.
Mrs Norman said the family thought the law was not protecting vulnerable people.
"No one's looking at these carers working in private homes," she said.
"We need cameras in people's homes to check what these carers are doing."
The case was discussed at a meeting of Bristol City Council's Adult Safeguarding Board on Wednesday night.
In a statement, the authority said: "We have taken action to address the general concerns raised by this case with the care agencies involved.
"Now the police investigations have concluded, we will work with the providers on any further specific issues raised."
Mrs Norman's father is now in a private residential home.
No charges will be brought against care workers who were under investigation in Bristol, the Crown Prosecution Service (CPS) has said.