Taxis drove at 5km/h (3mph) on the Tullamarine Freeway to Parliament House during the morning rush hour, causing a traffic jam.
The state government is planning industry reforms that will regulate ride-sharing app Uber and scrap taxi licenses.
Drivers are concerned they will not receive enough compensation.
Traditional taxis operate under rigid regulation and have to pay big sums for licences to drive passengers.
Last August, the state government legalised ride-sharing apps sparking a drop in the value of taxi operating licenses.