The invention discloses a milling and blasting combined construction method for a water-rich sandy 
dolomite stratum tunnel. The milling and blasting combined construction method aims to effectively reduce the risks of collapse, water inrush and mud gushing of an arch part under the condition of broken surrounding rock, control tunnel over-excavation and under-excavation, accelerate the construction progress, shorten the unit cycle construction time and effectively reduce the 
tunnel construction cost. The milling and blasting combined construction method comprises the following steps that (1) preparation work is performed before construction; (2) core soil of an upper step is excavated through weak blasting, an 
excavator of the upper step digs 
slag to a middle step and a lower step, reserved rock 
mass of the upper step is milled and excavated by adopting a 
cantilever excavator, and an upper step surrounding primary support is constructed in time after finishing to a designed outline; (3) core soil of the middle step is excavated through weak blasting, an 
excavator of the middle step digs 
slag to the lower step, a middle step left side reserved 
rock body and a middle step right sidereserved 
rock body are milled and excavated by adopting the 
cantilever excavator, and a middle step left side primary support and a middle step right side primary support are constructed in time afterfinishing to a design outline; (4) a 
rock body of the lower step is excavated through weak blasting, and a lower step left side primary support and a lower step right side primary support are constructed; and (5), a rock body of an inverted arch is excavated through weak blasting, and an inverted arch primary support is constructed.