Lexa Richards, whose grandmother Phyllis West had dementia, is urging people to register for the event to help the charity raise money for research and services.
Lexa, 42, and her partner Sylvia Ubych, from Worthing, have seen their lives transformed since Phyllis was diagnosed with dementia.
The pair are taking part in Brighton Memory Walk
and asking for supporters to follow suit by going to memorywalk.org.uk.
Lexa said: "My Grandmother had Parkinson's and dementia. It all accelerated after she suffered a stroke. She held on for 17 months and finally passed after a chest infection leading to pneumonia.
"My father, who was living with her as her carer, nursed her through the whole thing, even though he was going through treatment for prostate cancer.
"He refused to put her in a home and wanted to make her last days to be in her own home, but, due to the pneumonia, she had to be admitted into hospital. She was surrounded by six of her seven children and one grandchild – me.
"I'm looking forward to meeting up with like-minded people and just trying to help in my own way."
A total of 1,433 supporters have already registered to take part in the evnt, which will be on Saturday 30th September 2017.
More than 3,000 people in Brighton are living with dementia and last year's event – attended by 2,153 people – raised more than £222,000 to help people living with the condition.
Elisa Vaughan, Alzheimer's Society
operations manager for Sussex, said: "Dementia is set to be the 21st century's biggest killer.
"We are calling on family, friends – and furry four-legged supporters – to unite against dementia this autumn. Dementia devastates lives. Walk with us at Memory Walk and dementia won't win.
"Every pound raised will help Alzheimer's Society provide information and support, improve care, fund research and create lasting change for people affected by dementia."
Brighton Memory Walk on Saturday 30th September 2017. CLICK HERE for info.