The symbols were originally thought to be graffiti, but experts now believe they were carved to ward off evil spirits at Wookey Hole, Somerset.
Four new ritual protection marks were found by staff creating a new caving experience at the site.
Experts from Bristol University who have studied the markings said they dated from about 1550 to 1750.
Chris Binding from the university's speleological society, who helped carry out the survey, said about 50 carvings, which were originally thought to be mason's marks, were identified as being ritual protection marks in 2007.
He said the newly discovered markings, which were found in a more inaccessible part of the cave, had "all the characteristics of age".
"This is the largest known concentration of ritual protection marks in any cave in Britain," he said.
"It was a good luck charm in the medieval era and carried on through to the late 18th Century."
He added that most of the marks were in a vertical shaft - known as an aven - leading upward from a cave passage, which would have felt unnaturally cold to people below due to a convection draught.
The caves' owner, Daniel Medley, said the find "proved that the route our adventure cavers use is the same one used in the 15th Century, mentioned by William of Worcester in 1470".
He added: "It is quite chilling to think that people hundreds of years ago were deep underground carrying flaming torches for light and scratching these symbols on the rocks because they believed it would protect them from the witch and her evil."
Many of the symbols appear to be the letter W or the letter M, but it is thought they are double Vs, in reference to the Virgin Mary.
The marks will now feature in guided adventure tours at the attraction.
A series of witch markings have been discovered carved into walls at an underground tourist attraction.