Mark Worsfold, a martial arts trainer and former soldier, said that he was thrown to the floor and handcuffed just as cyclists passed by, Gulf News reported.
His worried wife Nicola only found out he was being held after she reported him missing when he did not turn up for their daughter's ninth birthday party.
The 54-year-old had his fingerprints, DNA and mugshot taken before being questioned about why he did not appear to be enjoying the event on July 28.
Police said Worsfold, who was held for over five hours, was arrested because of ''his manner, his state of dress and his proximity to the course.''
A spokesman added that the arrest was necessary to avoid a breach of the peace because he was standing near a group of protesters.
But Worsfold, who was diagnosed with Parkinson’s in 2010, said that one of the symptoms of the disease is muscle rigidity, which can cause his face to become expressionless and mask-like.
Worsfold, who had stopped to watch the men’s road race in Leatherhead, Surrey, after holding a Taekwondo demonstration nearby, said officers told him he was being arrested and taken to Reigate police station because he was not smiling.
''I was sitting minding my own business,'' he told a local newspaper.
''Before I knew anything the police grabbed me off this seven-foot wall, threw me to the floor and cuffed me so all I saw of the cycle race was between the feet of people from the pavement. It could have been done better. I was arrested for not smiling. I have Parkinson's,'' he said.
Worsfold, who lives in an 800,000 pound three-bedroom house in the picturesque village of Ockham near Woking, has since asked for a letter of exoneration from police.
Surrey Police said he was initially arrested on suspicion of a public order offence but was ''given words of advice'' before being ''released with no further action.''
A spokesman added that he was found to be in possession of a legal folding knife and several rubber knives which had been used for his Taekwondo demonstration.
The officers who made the arrest have apologised to him.