Here you go:

Dog Friendly Beaches - open all year

Porthcothan Bay
Treyarnon Bay
Constantine Bay
Harlyn Bay
Daymer Bay
Trebarwith Strand
Widemouth Bay - South Beach only
Summerleaze – Bude. Dogs on Lead (21st May - 30th Sept 10am-6pm)
Northcott
Sandymouth
Kingsand
Whitsand Bay
Downderry
Seaton
Plaidy Beach
Hannafore - West Looe
Talland Bay
Lantivet Bay
Lantic Bay
Mawgan Porth
Watergate Bay/ Whipsiderry
Great Western/Towan
Newquay Harbour
Little Fistral
Fistral
Crantock
Coombe Haven
Polridmouth Beach
Par Beach
Spit Beach
Hallane
Polstreath
Portmellon
Colona
Gorran Haven
Vault
Hemmick
Porthluney – Caerhays
Portholland
Polgwidden
Gillian Harbour
Porthallow
Porthoustock
Coverack
Kennack Sands - East
Cadgwith – East
Polpeor Cove
Pentreath
Mullion Cove
Gunwalloe
Loe Bar
Porthleven
Prussia Cove
West Portholland
Cellars Beach
Carne Beach
Pendower Beach
Porthcurnick Beach
Towan Beach
Porth Beor
Trevaunance Cove
Perranporth
Perran Sands
Holywell Bay
Long Rock
Eastern Green
Wherrytown
Roskilly
Salt Ponds
Pedn Vounder
Nanjizel
Gwenver
Priests Cove
Boat Cove
Portheras Cove
Hor Point
Clodgy Point
Bamaluz
Lambeth Walk
Porthkidney
Riviere
Mexico
Upton to Peter’s Point
Peter’s Point
Porthcew (Rinsey)
Kenneggy Sands

Seasonal Dogs bans – beaches which have a ban from Easter day to 1st October unless otherwise stated. Guide dogs are excepted from dog bans
Trevone Bay
St George’s Well
Polzeath Beach
Crackington Haven
Widemouth Bay (North Beach Only)
Crooklets
Cawsand Beach
Portwrinkle
Whitehouse Beach
Readymoney Beach
Polkerris Beach
Porthpean Beach
Tolcarne (1st May - 30th Sept)
Lusty Glaze (31st May - 30th Sept)
Porth Beach
Kennack Sands (West - near carpark)
Cadgwith Cove (South)
Housel Bay, The Lizard
Kynance Cove
Polurrian Cove
Poldhu
Gunwalloe Church Cove
Porthleven West
Pentewan (st November - Week prior to Easter)
Praa Sands
Portreath
Tattams Beach
Porth Beach
Summers Beach
Tavern Beach
Castle Beach
Gyllyngvase Beach
Swanpool Beach
Maenporth Beach
Porthtowan Beach
Chapel Porth
Perranuthnoe
Marazion (Chapel Rock to Long Rock Level Crossing)
Penzance Promenade (to Larigan River)
Mousehole (all year ban in harbour)
Porthcurno
Sennen Cove (including harbour)
Porthmeor
Porthgwidden
St Ives Harbour
Porthminster
Carbis Bay
Hayle Towans (from Hayle River to Black Cliffs)
Gwithian (Ceres Rock to Red River)
Godrevy (Red River to lighthouse)
Porthgwarra
Porthchapel (dog ban applies below high water mark only)

See also:
http://www.cornwall-beaches.co.uk/dog.php
http://www.visitcornwall.com/xsdbimgs/D … LowRes.pdf