Abstract: Abnormal chloroplast division homozygous mutant strain parc6 and albinistic cotyledon homozygous mutant strain sco2 were identified at the DNA, RNA and cellular levels, while the effects of chloroplast abnormal division on the growth of cotyledon and leaf were investigated by adding different concentrations of sucrose to the medium and taking sl2, the double mutant with leaf abnormal division and cotyledon albino as the control. The results showed that the cotyledon of sco2 mutant was albino, while the leaf grew normally. Meanwhile, the cotyledon growth and viability of the parc6 mutant were significantly lower than the wild-type, which was equivalent to the sco2 mutant, however, the double mutant sl2 with cotyledon albinism and leaf abnormal division was severely hindered. The leaf growth and viability of the parc6 mutant were also significantly lower than that of the wild type, but recovered compared to the cotyledon. The inhibited cotyledon growth phenotype of the parc6 mutant and sco2 mutant could be confirmed by the addition of carbon source to the medium, but chloroplast fluorescence parameters of sco2 were different from the wild type. The results of BN-PAGE combined with SDS-PAGE showed that the high-level structure of the photosystem of the cotyledon and leaf were normal, indicating that chloroplasts of parc6 failed to produce enough energy to affect the growth of cotyledon and leaf. The phylogenetic analysis showed that PARC6 and SCO₂ coevolved, suggesting a connection between cotyledon development and chloroplast division. Our results indicated that chloroplast size was closely related to plant growth, especially the development of cotyledon, which provided a new perspective for revealing chloroplast function.