We carried out to better understand calcium behavior in plant growing in media with different calcium levels, deficiency (3), normal (1), and surplus (3). Growth of cucumber plants did not appear significant difference among calcium levels by 7 days after transplanting, but growth rate at 14 days was the highest in normal and followed deficiency and surplus. Increase in calcium concentration treated resulted in not only an excessive Ca uptake of plant but also a proportional decrease in Mg contents. In addition, excessive absorbed Ca was preferentially accumulated in stem and root to avoid leaf damage. Oxalate playing a role as a mediator of excessive Ca through Ca-oxalate crystal formation in cell was analyzed. Oxalate content in leaves was proportionally increased with an increase in calcium level in media, and the correlation coefficient was 0.94(>0.001), while Ca and oxalate in stem and roots did not show significant relation. Ca-oxalate crystal isolated from different Ca-treated leaves and stem was observed using SEM-EDX. Large amount of Ca-oxalate crystal was formed with an increase in Ca concentration. This means that excessive Ca in cell is immobilized through the formation of Ca-oxalate crystal with oxalate bio-synthesized.