Shocking footage captured the moment his friend Mr Liu, said to be a local mayor, turned up at his home to be greeted by his wife, Cui Hua, who he knew though work.
The footage, captured in August 2016 but only recently shared, shows the pair kissing as they greet.
They then a brief conversation before Mr Liu appears to start undressing her.
Mr Yang explained he had been hiding the incident as his son was preparing for university entrance exam and only decided to divorce in January 2018.
Mr Yang said he had complained to the local government but had yet received any reply.
Being accused of cheating, Cui Hua replied to ShangYao News that she was a colleague of Mr Liu.
She admitted that the government had received her ex husband’s complaint and said: “If this is true, they [the officials] would have given me a warning.”