The chromosome numbers of six species of Chinese Melastoma L. and Tibouchina Aubl. in Melastomataceae and karyotypes of four speices of Melastoma were investigated. The results showed that the four Chinese Melastoma species was found to be diploid with the chromosome number 2n=24. The chromosome number of Tibouchina urvillean and T. heteromall was 2n=36. The karyotype formulae were as follows: M. malabathricum 2n=10m(2SAT)+14sm; M. sanguineur 2n=10m+12sm+2st; M. dodecandrum 2n=12m+12sm; M. intermedium 2n=12m＋10sm+2st. The karyotype analysis showed that the chromosomes in Melastoma were short in length, ranging from 0.43 to 1.79 µm. The arm ratios of all the chromosomes were larger than 2. The karyotypes were of Stebbins’s 2B type. The karyotypes of Melastoma were reported for the first time.