The invention relates to an iron-cobalt-nickel alloy cold rolling strip with grain size number of grade 6-9 and a production method thereof. The iron-cobalt-nickel alloy cold rolling strip comprises the following chemical components by mass percentage: less than or equal to 0.03% of C, less than of equal to 0.020% of P, less than or equal to 0.020% of S, less than or equal to 0.50% of Mn, less than or equal to 0.30% of Si, less than or equal to 0.20% of Cu, less than or equal to 0.20% of Cr, less than or equal to 0.20% of Mo, 28.5-29.5% of Ni, 16.8-17.8% of Co, and the balance of iron; during production of steel ingot smelted by the iron-cobalt-nickel alloy, melting temperature can reach more than 1500 DEG C, at least one of the rare earth elements of Ce and La is added before steel tapping during melting is taken as a catalyst, weight of the added rare earth element accounts for 0.05-0.2% of total weight percentage of the ingredients, a multi-pass rolling technology is employed during subsequent hot rolling and cold rolling, grain size of the rolling strip is more uniform, and oversize grade difference of the crystal grain can be avoided.