Zane Gbangbola died at his home in February as flood waters rose.
A post-mortem proved inconclusive, but a pathologist said the seven-year-old had been killed by carbon monoxide poisoning yet no test results have provided any evidence of this theory.
There is controversy around Zane's death as his parents believe he died from hydrogen cyanide poisoning.
They allege it was in the flood water, which they say had passed through a landfill site.
As part of its investigation, Surrey Police seized a petrol-driven pump from inside the house.
The force has been trying to establish whether there is any liability or criminal offences in respect of the hire company who provided the equipment.
After submitting a file to the Crown Prosecution Service, it was decided there is no criminal case to answer.
Senior investigating officer Detective Inspector James Norbury, said: "The death of seven-year-old Zane was an extremely tragic event and our thoughts remain with his family.
"We have received advice from the Crown Prosecution Service and no criminal charges will be brought in relation to this case.
"The process was lengthy and we fully appreciate it has been a frustrating and painful time for all concerned while enquiries were carried out.
"Officers have met with Zane's parents throughout the investigation and provided as much information as possible at each stage and they have been updated as to the results of our investigation.
"We will now share our findings with Coroner."
Zane's parents have never believed the pump was the cause of their son's death.
They have launched a campaign called 'Truth About Zane'.
In response to today's announcement, the Gbangbola family have released a statement: "Nicole and Kye have always maintained that there could be no criminal proceedings against the pump company as the only pumps in use were electric.
"They are now hopeful that there will be a proper investigation and testing of the old landfill site next to Zane's home to determine how Hydrogen Cyanide got into their flooded home and into the blood of the whole family the night Zane tragically died."