Abstract：The chromosome numbers and karyotypes of 12 Forsythia species and cultivars were studied using squashing method, and the results showed that 11 other Forsythia species and cultivars were diploid (2n=2x=28), except F. intermedia ‘Goldrausch’, which was tetraloid (2n=4x=56). The karyotypes of F. suspensa, F. ovate, F. mandshurica and F. koreana were 2A, 3B, 2B, 3B, separately. The karyotypes of 6 F. intermedia cultivars included 2A, 2B and 3B. The karyotypes of 2 F. koreana cultivars included 2B and 3B. Generally, the centromere index of 12 Forsythia species and cultivars were not distinct different, which arranged from 9.65% to 50.00%. The karyotypes of all the tested Forsythia taxa were mainly made of m, sm, and st, without chromosome or satellite The results from clustering analysis on karyotype parameters of the 4 Forsythia species showed that F. suspense and F. mandshurica have near genetic relationship, while the genetic relationship between F. suspense and F. ovata was distant. Meanwhile, F. intermedia cultiawrs have nearer genetic relationship with F. mandshurica and F. koreana, than F. suspense and F. ovata. The results provided cytological information for genetic relationship analysis and parent selection in interspecific hybridization in Forsythia genus.