He said that Labour needed to stop defining itself by its opposition to the SNP and the Tories.
The politician also called for a major overhaul of the party's rules on leadership elections.
Mr Macintosh is running against Kezia Dugdale, the party's current deputy leader, who announced she was standing in May.
Labour's current leader, Jim Murphy, said he would resign this month, after Labour's poor performance at the general election, despite winning a vote of no confidence.
Mr Macintosh, who has represented the Eastwood constituency since 1999 and is Labour's social justice spokesman at Holyrood, launched his candidacy after meeting students at Glasgow University.
He said the Labour Party in Scotland had "lost the trust and the faith of the people of Scotland" and needed "to take a fundamentally different approach" to politics.
Mr Macintosh added: "I do not want to ask people to vote Labour to block the Tories in London or to stop the SNP in Edinburgh; I want them to want to vote Labour because we have the ideas, the vision and the values to deliver a better future for Scotland.
"Devolution offers a new way of doing politics in Scotland, less tribal and confrontational, more collaborative, more about sharing power with civic Scotland, with the voluntary sector, with businesses, with the people of Scotland.
"That is why I am standing to be leader of Scotland's Labour Party. It is time we focus on Scotland's future, not Labour's past."
Mr Macintosh, who has stood for the leadership in 2011, said he would be a "reformist" leader, and called on party members and affiliated organisations to support his proposals to change the rules of electing a new leader.
He has set out his proposals, which include;
Mr Macintosh has also said he wanted to move to a "one member one vote" system for electing party leaders, rather than the three-college system currently used by the Labour.
He also favours introducing open primaries, in which candidates could be questioned by registered supporters of the party rather than just paid-up members.
Tensions have already mounted in the leadership contest, with Mr Macintosh having accused the "party machine" of bullying his supporters in an attempt to avoid a contest.
He said his comments had not been aimed at party staff, but he has not named those he thought were responsible.
Kezia Dugdale has already secured the support of more than half of Scottish Labour's MSPs, as well as MP Ian Murray, since announcing her intention to stand.
Labour MSP Ken Macintosh has officially launched his bid for the party's leadership in Scotland.