The invention discloses a low-cost extra-deep-drawing-quality cold-rolled galvanized steel strip and a preparation method thereof. The steel strip is prepared from, by mass percent, 0.001% to 0.005% of C, 0.07% to 0.12% of Mn, not larger than 0.012% of S, not larger than 0.012% of P, not larger than 0.03% of Si, 0.010% to 0.060% of Als, not larger than 0.0040% of N, 0.0015% to 0.0030% of B and the balance Fe and inclusion within an allowed range. According to the galvanized steel strip, the reasonable carbon content is controlled to reduce the content of free carbon in steel as much as possible; and meanwhile, a certain amount of boron is added to fix interstitial nitrogen and part of carbon, and therefore the timeliness of an extra-deep-drawing-quality galvanized product can be guaranteed. According to the galvanized steel strip, boron is used for fixing carbon atoms, so that the cost of an alloy material is greatly reduced, meanwhile, the heating temperature and soaking temperature of a galvanization procedure can be greatly reduced, and therefore production difficulty and energy consumption are effectively lowered.