The report released Monday shows that major changes to the fund could cause greater harm.
Last year the Republican-led Legislature ordered the Department of Administration and Department of Employee Trust Funds to conduct a study into whether proposed changes to the pension fund would benefit the state.
The proposed changes included a new 401-k-type program and the possibility for state and local employees to decide not to contribute to the fund.
The new state study shows these changes could come at a greater cost to taxpayers while decreasing benefits to currrent and future retirees.
This report was highly anticipated after a Pew Center study released in June showed Wisconsin had the healthiest state pension fund in the nation.
Gov. Scott Walker responded to Monday's report saying, "The report released today confirms that both taxpayers and pensioners are getting a great deal with the WRS."
Many Democrats and state employees had been concerned the Walker administration would institute changes in order to cut costs and balance the state budget.
"I WANT TO BE VERY CLEAR: I AM CURRENTLY NOT PLANNING TO MAKE ANY SUBSTANTIAL CHANGES TO THE WRS.