The invention relates to a continuous annealing production method of cold-rolled sheet No.45 steel. The steel comprises the following components in percentage by weight: 0.47 percent of C, 0.60 percent of Mn, 0.31 percent of Si, less than or equal to 0.035 percent of P, less than or equal to 0.035 percent of S, less than or equal to 0.025 percent of Cr, less than or equal to 0.025 percent of Ni, less than or equal to 0.025 percent of Cu and the balance of Fe. In the method, the heating temperature of a hot rolling process is controlled to be 1,250+/-30 DEG C, the final rolling temperature is 900+/-20 DEG C, the reeling temperature is 730+/-20 DEG C; and the cold rolling down rate of a cold rolling process is controlled to be 50-70 percent. The continuous annealing process comprises the following steps of: putting band steel into a nonoxidative atmosphere consisting of H2 and N2 as a medium in a furnace from room temperature and heating up to 240-260 DEG C through 37-52 seconds; further heating up to 750-770 DEG C through 670-850 seconds; preserving heat for 214-300 seconds; cooling to 590-610 DEG C through 60-85 seconds; cooling to 440-460 DEG C through 13-19 seconds; and cooling to 390-410 DEG C through 789-1,105 seconds, and then cooling to room temperature with water. A continuous annealing steel plate produced by the invention has higher strength and elongation, thus the product quality is improved.