The event's patron, he attended the 10th annual memorial service and joined a reception for officers and their families at Cardiff's St David's Hall.
Among those honoured were Nicola Hughes and Fiona Bone, the two PCs brutally murdered in a gun and grenade attack in Greater Manchester last year.
The prince said the deaths reinforced how dangerous the job could be.
“Our courageous policemen and women routinely endure hazardous environments in order to defend us and protect all our freedoms,” he said in a statement.
“But there is nothing routine about the courage they display.
“They will never be forgotten and their proud legacy inspires us and will always live on.”
Bryn and Natalie Hughes – the father and stepmother of PC Hughes – said the day was hugely important.
Mr Hughes said: “It means our sacrifices, like Nicola and Fiona, don't go forgotten by the general public.
“There was times of immense sadness mixed with times of such strength and courage.
“It is humbling when you hear your daughter's name read out at such a service, you almost want to turn to her and say 'that's your name'.”
Mr and Mrs Hughes said a petal from the thousands that fell as part of the service stuck to each of them.
Mrs Hughes said: “One landed on my shoulder and I thought 'that's Nicola'.”
Prince Charles is patron of the National Police Memorial Day service, which Wales was hosting for the second time.
He was greeted by a mounted police honour guard on his arrival in Cardiff, and also received cheers from the public who had gathered outside the hall.
Home Secretary Theresa May and First Minister Carwyn Jones, who said the sacrifice of officers would not be forgotten, both took part in the service, giving readings.
Metropolitan Police officer PC Andrew Duncan, 47, who was killed in a suspected hit-and-run collision a week ago, was also remembered.
Home Secretary Theresa May said: “The tragic death of PC Andrew Duncan brings home the importance of National Police Memorial Day, when we come together to remember the debt of gratitude we owe to policemen and women across the country who put themselves in harm's way to protect us.
“PC Duncan gave more than 20 years' service to the people of London and was described by colleagues in the Metropolitan Police as both courageous and hard working.”
The event moves around the countries of the UK each year and was last held in Cardiff in 2009.
First Minister Mr Jones said: “It is a privilege to host the 10th annual memorial service in Wales again this year.
“The police service makes an immeasurable contribution to our society for which we are all very grateful.
“Sadly, each year police officers give their lives making sure that we can all live in safety.
“The memorial service is an opportunity for us all to remember those officers and to ensure that their relatives, friends and colleagues know their sacrifice is not forgotten.”
Steve Williams, chairman of the Police Federation of England and Wales, said: “Policing can sometimes be very dangerous. When people go to work you expect them to come home at the end of the day. Sometimes in the policing world, this is not the case.
“It is right that the public are reminded of the dedication to duty.
“I am so proud to be here today as a Welshman. It is being held in Wales, we have the Prince of Wales here – it means a great deal.”
National Police Memorial Day was founded in 2004 by Sgt Joe Holness QPM.
Sgt Holness said around 4,000 police officers had given their lives in the line of duty since modern policing records began in 1792.
“There are between 10 and 15 fallen officers every year,” he said. “It is not too much to ask for one day a year to be set aside to remember their commitment to the public.”