The invention provides an early warning method of material instability type roadway rock burst based on bulging amount critical state, which comprises the following steps of: S1, establishing a calculation model of the critical value of the bulging amount of the roadway rock burst; S2, collecting the parameters of the roadway to be judged, bringing the parameters into the calculation model of thecritical value of the bulging amount, and calculating to obtain the critical value of the bulging amount of the rock burst of the roadway to be judged; S3, collecting the actual bulging amount of thesurrounding rock of the roadway to be judged, comparing the actual bulging amount with the calculated critical value of the bulging amount, and carrying out early warning on the rock burst of the roadway according to the comparison result; according to the method, the critical state of the roadway material instability type rock burst can be characterized by calculating the maximum elastic bulgingamount, the calculated maximum elastic bulging amount is used as a threshold value for early warning and judging the roadway rock burst, the roadway rock burst triggering can be accurately and quicklycarried out for early warning, the method can be widely applied to field engineering guidance, the occurrence of impact accidents is avoided or reduced, and the safe production of mines is ensured.