An ultra-heavy steel plate with low cracking sensitivity and low yield ratio, the mass percentages of chemical components of the steel plate are C 0.05-0.09; Si 0.2-0.4; Mn 1.3-1.6; Al 0.02-0.04; Nb 0.03-0.08; V 0.03-0.08; Cr 0.1-0.5; Ni 0.1-0.5; Mo 0.1-0.3; Cu 0.2-0.5; Ti 0.01-0.02; P≤0.015; S≤0.003; N≤0.007, the balance being Fe and inevitable impurities; the carbon equivalent is ≤0.43, the cold cracking sensitivity coefficient Pcm is ≤0.20. A low cracking sensitivity and low yield ratio steel plate with a thickness of 40-70 mm is manufactured by the process steps of KR molten iron pretreatment-converter smelting-LF refining-RH vacuum degassing-continuous casting-lid-covering slow cooling for the continuous casting slabs-casting slabs heating-controlled rolling-controlled cooling-hot straightening-air cooling and so on.