The invention relates to a telescopic arm open-cut rock drilling jumbo with a drill rod replacing device. The telescopic arm open-cut rock drilling jumbo comprises a cab, a chassis assembly, a propeller assembly, a telescopic arm, the drill rod replacing device, a rock drill, a control system and a power and air control system 36; the cab is arranged on a cab bottom plate of the chassis assembly, the control system is arranged in the cab, and the control system is connected with the power and air control system; the telescopic length, the pitching angle and the deflection angle of the telescopic arm, the elongation of a propelling beam and the pitching angle of the cab are controlled by the control system; the arm seat of the telescopic arm is fixedly arranged at the front end of the cab, the propelling beam is in sliding fit with the telescopic arm through a bracket on a compensation cylinder, the telescopic end of the compensation cylinder is fixedly connected to the propelling beam, and extending compensation of the propelling beam can be realized by stretching of the compensation cylinder; and the drill rod replacing device is fixed on the propelling beam and positioned below a transmission rod, and the rock drill is fixed at the upper end of the propelling beam. The multi-azimuth drilling requirement of the jumbo can be met, and the gravity center of the whole jumbo is kept stable.