This study explored the mechanism of Zn-methionine (Zn-Met) influencing eggshell quality of laying hens, and investigated whether the mechanism was related to calcium deposition. Hyline Grey layers (n 384, 38 wk) were divided into four groups: 0 mg Zn/kg, 40, 80 mg Zn/kg as Zn-Met, 80 mg Zn/kg as zinc sulfate (ZnSO4). Eggshell quality, zinc contents, zinc-containing enzymes activities and expressions of shell matrix proteins in eggshell gland (ESG) were analyzed. 80 mg/kg Zn-Met treatment increased (P < 0.05) egg weight and eggshell strength throughout the experiments. 80 mg/kg Zn-Met (P < 0.05) group decreased mammillary knob width and had larger relative atomic weight percentage of Ca, stronger signal intensity of Ca in linear distribution, and the Ca was more evenly distributed in transversal surface of eggshell. Zn contents (P < 0.001) in yolk and serum, Ca, albumin (Alb) levels in ESG as well as carbonic anhydrase (CA) activity in serum (P < 0.05) and mRNA levels of CA and Ca-binding protein-d28k (CaBP-D28k) (P < 0.001) in 80 mg/kg Zn-Met group were the highest among all treatments. In conclusion, shell strength as one of eggshell qualities was mostly related to mammillary cones width in ultrastructure caused by the pattern of calcium deposition in eggshell formation. And the increase of Zn-Met-induced calcium deposition may be due to the increased zinc contents in serum and tissues which were attributable to the increased CA concentrations in serum, Ca, Alb levels and up-regulated CA and CaBP-D28k mRNA levels in ESG.