Carbonic anhydrase (CA, EC 188.8.131.52) is a Zn-containing enzyme and catalyzes the conversion between CO2 and HCO3-. CA play important roles in inorganic carbon metabolism, ion balance, pH stabilization and water balance and widely exist in archaea, bacterium, animal and high plants. Basing the amino acid sequences CA can be divided into four groups including alpha, beta, gamma and delta. So far, all the members discovered in animal belong to alpha group and the other species belong to alpha, beta and gamma; the only one member belongs to delta group was reporter in diatom. In this study, one T-DNA insertion CA mutation, which exhibited a phenotype of dwarf, was isolated in rice (Figure 1). The RT-PCR result indicated a constitutive gene expression profiles in every tissues (Figure 2). The blastn result of T-DNA flanking sequence showed the T-DNA was inserted into the fourth intron (Figure 3) and the insertion event result in a complete knockout of gene expression and decrease most of CA activity in vitro (Figure 4). The further GS data suggested this gene involved in CO2 assimilation and responding.