The reason is very simple, he said on the sidelines of the World Economic Forum in Davos, Switzerland: "People want a change."
The elections later this year would mark the first time a civilian government has completed a full five-year term and transferred power through the ballot box in Pakistan. Past governments have been toppled in military coups or dismissed by presidents allied with top generals.
Although few expect a coup this time, there is widespread unhappiness with the ruling Pakistan People's Party's performance at a time when the country is plagued by high unemployment, rampant energy shortages and frequent attacks by Islamist militants.
Mr Khan said the party he founded 15 years ago after retiring from professional cricket - Tehreek-e-Insaf or the Movement for Justice - now has 10 million members, most of them young people and women.
He estimated that 40 million young Pakistanis will be voting for the first time in the elections, out of a registered electorate of 90 million, and said they are "the engine for change".
But he predicted an "epic battle" by the "political class" and parties that have a vested interest in preserving the current "crumbling system" and status quo to stop change.
He said he does not think the country's powerful army will be part of this campaign, which would be a first. He has in the past denied allegations that his movement is backed by Pakistan's powerful military.
The former cricketer - who few analysts expect to outright win the polls - accused the entrenched Pakistani political parties of closing ranks and giving huge amounts of money to the media to criticise his party.
He said his party is currently holding internal elections - a rarity in Pakistan.