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The 59-year-old revealed last December that he had been diagnosed with a rare form of the disease.
He slammed the lack of funding available to sufferers during a speech at the Alzheimer's Research Trust conference in Bristol, saying he wanted to "kick a politician in the teeth".
He said: "There's nearly as many of us as there are cancer sufferers, and it looks as if the number of people with the disease will double within a generation. It's a shock and a shame, then, to find out that money for research is 3% of that which goes to find cancer cures.
"Perhaps that is why, for example, that I know three people who have successfully survived brain tumours but no-one who has beaten Alzheimer's."
Pratchett will give the money to the Alzheimer's Research Trust charity.
He is best known for the popular Discworld series, which currently comprises 36 novels.
