Irregular Shaped Voltage Islands (ISVI) can achieve much better power savings in multiple supply voltage (MSV) technology. This paper proposes a simulated annealing (SA) based floorplanning method with ISVI generation using a Hazard and Heal strategy. In each perturbation of SA, a randomly chosen block is removed from floorplan and then inserted back to a proper position, to join certain voltage island. The solution space for every iteration is O(n2kvi), where n is block number and kvi is voltage island number. Every position with voltage island assignment is evaluated by a linear combination of chip area, wire length, power and voltage island cost. To avoid timing-consuming evaluation of O(n2kvi) possibilities, we propose a fast Hazard method to construct ISVI by skipping lots of distant voltage island candidates while occasionally accepting seldom-emerged illegal (non-contiguous) candidates. To resolve the seldom-emerged non-contiguous voltage islands, a detailed Heal method is applied in each temperature. Experimental results show the proposed method is effective and efficient compared with the latest works.