The invention discloses a low compression ratio 690MPa grade extra thick steel plate and a production method thereof, and the low compression ratio 690MPa grade extra thick steel plate comprises the following components by weight: 0.05%-0.14% of C, 0.12%-0.45% of Si, 0.70%-1.40% of Mn, < = 0.010% of P, < = 0.005% of S, 0.025%-0.065% of Als, < = 0.005% of N, 0.10%-0.50% of Cu, 0.50%-1.00% of Ni, 0.10%-0.40% of Cr, 0.10%-0.45% of Mo, also comprises one or more than two components selected from the following chemical components: 0.03%-0.08% of V, 0.005%-0.04% of Nb, 0.005%-0.03% of Ti, 0.0008-0.004% of B and 0.002%-0.006% of Ca, and also comprises balance of Fe and inevitable impurities, wherein the total ratio of precious and strengthening elements of Cr, Mo, Ni and Cu is less than or equal to 1.5%.