The invention relates to the field of machinery, in particular to a seven-degree-of-freedom hydraulic heavy-load mechanical arm. The seven-degree-of-freedom hydraulic heavy-load mechanical arm comprises a rotary joint, a lifting joint, a telescopic joint, a horizontal swinging joint, an advancing and retreating joint, a rolling joint, a pitching joint and a clamping mechanism, wherein the rotary joint comprises a base and a rotary table capable of rotating by 360 degrees on the base, the lifting joint is arranged on the rotary table, the lifting joint, the telescopic joint, the horizontal swinging joint, the advancing and retreating joint, the rolling joint, the pitching joint and the clamping mechanism are sequentially connected, the lifting joint and the telescopic joint are in sliding connection, and the horizontal swinging joint and the advancing and retreating joint are in sliding connection. The mechanical arm can realize rotating, lifting, stretching, horizontal swinging, advancing, retreating, rolling, pitching and grabbing actions, the working range of the mechanical arm is expanded, the problem that the precision of the heavy-load mechanical arm is low is solved, obstacles are effectively avoided, movement paths of the mechanical arm are more flexible, and the anti-explosion and fireproof capability of the mechanical arm can be effectively improved through full-hydraulic driving.