The invention discloses a 50-150 mm thick high-strength ship plate steel EQ5 thick plate and a production method thereof. The high-strength ship plate steel EQ51 thick plate is prepared from chemical ingredients in percentage by mass as follows: 0.04%-0.06% of C, 0.10%-0.15% of Si, 0.9%-0.95% of Mn, smaller than or equal to 0.018% of P, smaller than or equal to 0.005% of S, 0.020%-0.045% of Als, 0.31%-0.39% of Cr, 0.14%-0.19% of Mo, 0.21%-0.23% of Cu, 0.075%-0.085% of Nb, 0.31%-0.41% of Ni, 0.0020%-0.0030% of Ca and the balance of Fe and residual elements. A technological process of the high-strength ship plate steel EQ51 thick plate is shown as follows: pretreatment of high-quality molten iron and KR molten iron, refining in a 100/120 ton top-bottom combined blowing converter and an LF (ladle furnace), vacuum degassing treatment, 24-60 h pile cooling of a casting blank, treatment in a pusher type heating furnace, treatment with a 3800 m rolling mill, ACC laminar cooling, 11-roll hot straightener, pile cooling and quenching-and-tempering heat treatment, finishing, external examination, flaw detection and storage. The high-strength ship plate steel EQ51 thick plate and the production method have the benefits as follows: compared with a conventional EQ51 production process, the method ensures that the performance of a steel plate can meet standard requirements; besides, the problem that 80 mm or thicker steel plates cannot be produced through continuous casting is solved, the production cycle is shortened, and the production energy consumption is low.