The invention belongs to the technical field of industrial robot application, and discloses a pure mechanical drive type spray painting robot. The pure mechanical drive type spray painting robot comprises a five degree-of-freedom robot and a positive pressure explosion protection system. The five degree-of-freedom robot comprises a fixed base, a rotary base, a rotary driving device, a tail end installation seat, a spray gun, a position adjusting rod group, a posture adjusting rod group and synchronous wheel drive. The position adjusting rod group comprises a servo motor, a big arm, a front arm, a small arm and a small arm pull rod; the posture adjusting rod group comprises an electric sliding table, an electric cylinder fixed seat, a first posture protection rod, a triangle connecting frame, a second posture protection rod and a spring supporting rod; the synchronous wheel drive comprises the servo motor, a synchronous pulley and a synchronous belt; and the positive pressure explosionprotection system comprises an air pump, an air pipe and a sealing shell. A pure mechanical drive scheme is adopted, electrical parts are placed on bottoms of robot bases and branched chains, integralexplosion protection is carried out, the production efficiency is high, the safety performance is high, and automatic spray painting operation can be realized.