A high-strength thick steel plate for a pipeline having excellent low-temperature toughness and elongation and a low yield ratio comprising, by wt%, 0.03 to 0.055% of C, 0.1 to 0.35% of Si, 1.7 to 2.2% of Mn, 0.01 to 0.04% of Al, 0.005 to 0.025% of Ti, 0.008% or less of N, 0.08 to 0.12% of Nb, 0.2 to 0.45% of Cr, 0.2 to 0.35% of Ni, 0.05 to 0.3% of Cu, 0.2 to 0.4% of Mo, 0.02% or less of P, 0.002% or less of S, 0.0005 to 0.004% of Ca, 0.01 to 0.04% of V, 0.0005% or less of B, a balance of Fe, and other inevitable impurities, and satisfying Relational expressions 1 to 4, wherein a microstructure of the steel plate comprises, by area%, 1 to 5% of polygonal ferrite, 60 to 75% of acicular ferrite, 20 to 30% of bainitic ferrite, and 5% or less of martensite-austenite constituent, and wherein the polygonal ferrite has an average effective grain size of 13 μm or less, and wherein the bainitic ferrite has an average effective grain size of 14 μm or less, and wherein the martensite-austenite constituent has an average effective grain size of 0.8 μm or less, wherein a yield strength in a direction of 30° with respect to a rolling direction is 550 MPa or more, a tensile strength is 660 MPa or more, a yield ratio is 0.83 or less, a separation length at - 10°C is less than 5 mm, an impact energy at -10°C is 320 J or more, a total elongation is 42% or more, and a minimum temperature at which a drop weight tearing test (DWTT) percent ductile fracture of 85% or more is satisfied is -30°C or lower, and 19 ≤ Mo / 96 / P / 31 ≤ 30 1.42 ≤ Cr + 2 Mo + Cu + Ni + 1000 B ≤ 1.75 4 < 3 C / 12 + Mn / 55 × 100 ≤ 4.9 600 ≤ 400 C + 6800 Nb + 600 V + 800 Ti + 300 Al ≤ 820 where, contents of the alloying elements described in Relational expressions 1 to 4 are wt%. comprising, by wt%, 0.03 to 0.055% of C, 0.1 to 0.35% of Si, 1.7 to 2.2% of Mn, 0.01 to 0.04% of Al, 0.005 to 0.025% of Ti, 0.008% or less of N, 0.08 to 0.12% of Nb, 0.2 to 0.45% of Cr, 0.2 to 0.35% of Ni, 0.05 to 0.3% of Cu, 0.2 to 0.4% of Mo, 0.02% or less of P, 0.002% or less of S, 0.0005 to 0.004% of Ca, 0.01 to 0.04% of V, 0.0005% or less of B, a balance of Fe, and other inevitable impurities, and satisfying Relational expressions 1 to 4, wherein a microstructure of the steel plate comprises, by area%, 1 to 5% of polygonal ferrite, 60 to 75% of acicular ferrite, 20 to 30% of bainitic ferrite, and 5% or less of martensite-austenite constituent, and wherein the polygonal ferrite has an average effective grain size of 13 μm or less, and wherein the bainitic ferrite has an average effective grain size of 14 μm or less, and wherein the martensite-austenite constituent has an average effective grain size of 0.8 μm or less, wherein a yield strength in a direction of 30° with respect to a rolling direction is 550 MPa or more, a tensile strength is 660 MPa or more, a yield ratio is 0.83 or less, a separation length at - 10°C is less than 5 mm, an impact energy at -10°C is 320 J or more, a total elongation is 42% or more, and a minimum temperature at which a drop weight tearing test (DWTT) percent ductile fracture of 85% or more is satisfied is -30°C or lower, and 19 ≤ Mo / 96 / P / 31 ≤ 30 1.42 ≤ Cr + 2 Mo + Cu + Ni + 1000 B ≤ 1.75 4 < 3 C / 12 + Mn / 55 × 100 ≤ 4.9 600 ≤ 400 C + 6800 Nb + 600 V + 800 Ti + 300 Al ≤ 820 where, contents of the alloying elements described in Relational expressions 1 to 4 are wt%. <EOS>