对φ4m×12m的三鞍座卧式圆筒形低压容器的受力进行了分析，并给出了其弯矩、剪刀、支座反力与各项应力（轴向应力、周向应力、切应力）的计算公式及其计算结果，并与两鞍座卧式圆筒形容器的计算结果进行了对比。对比结果表明，采用三鞍座结构，筒体壁板厚度可由两鞍座的24mm减小到20mm，单台容器可节约钢材8．3t；并改善了筒体的受力状况，尤其可使对筒体设计起决定作用的周向应力大为减少，而且完全符合GB150-89之规定。 The force of the horizontal saddle with a diameter of 4m × 12m and the horizontal cylindrical low pressure vessel with three saddles are analyzed. The bending moment, scissors, bearing reaction force and stress (axial stress, circumferential stress, Stress) and its calculation results are compared with those of two saddle horizontal cylindrical vessels. The comparison results show that the thickness of the cylinder wall can be reduced from 24mm to 20mm with two saddles, and 8.3t can be saved in a single container by using the three-saddle structure, and the stress condition of the cylinder can be improved. In particular, Cylinder design plays a decisive role in the circumferential stress greatly reduced, but also in full compliance with the provisions of GB150-89.