【Objective】 The study aims to definite the karyotypic characteristics and genetic relationships of 12 species of Oxalis from a cytology of view, to provide a reference for exploring the chromosome diversity of Oxalis, identifying the germplasm resources of Oxalis, and selecting the parents for cross-breeding. 【Methods】 The chromosome morphology, number and karyotype of 12 species of Oxalis plants were observed and analyzed by applying the root-tip compression method. 【Results】 The results showed that: (1) Chromosome numbers are reported for the first time for seven species, and of the five reported species, O. fabaefolia and O. pes-caprae have chromosome numbers consistent with previous reports, while the remaining three, differ from previous reports, of which 2n=26 was the first reported chromosome number in the genus Oxalis. A total of seven chromosome bases were found, of which x=13 was reported for the first time; ploidy ranged from 2x to 6x, actual chromosome sizes ranged from 0.27 μm to 2.23 μm, and the location of the attachment point was the metacentric (m) and submetacentric (sm) chromosomes. There were four karyotype types and the karyotype asymmetry coefficients ranged from 56.31% to 65.40%. (2) Among them, O. fabaefolia was the most evolved, and O. compressa was the most primitive. (3) According to the similarity of chromosomal karyotypes, the 12 species of Oxalis can be divided into four groups. 【Conclusion】 It was concluded that the 12 species of Oxalis had extensive karyotypic diversity and that the results of the karyotypic classification were not in complete agreement with the morphological classifications of the previous researchers.