Plant communities in urban parks provide essential ecological services for the urban ecosystem. Based on the field survey of six most representative coastal urban parks in Shenzhen, and combined with high-resolution remote sensing images, the characteristics of plant community structure and its correlation with the internal landscape pattern of the parks were analyzed. The features of plant community structure and its relationship with the internal landscape patterns of the parks were analyzed. The results showed that: (1) A total of 471 plant species belong to 108 families and 310 genera were investigated, among which 231 species were native plants from 169 genera and 82 families. The proportion of native plants is higher in herbaceous plants, while the proportion of native plants is lower in woody plants. (2) TS-4 and H-1 were respectively the most common arbor-shrub community type and herbaceous community type, with their sample plots accounted for 39% and 26% of the total plots, respectively. Most indicator species of frequent communities were tropical and dominant species. (3) The species richness of shrub plants in the parks was lower than arbor and herbaceous plants, but the community stability was higher. (4) The lowest similarity of plants appeared in shrubs between semi-natural and artificial offshore parks. (5) In the overall landscape pattern of the parks, patch density was negatively correlated with the ratio of forest area and the area ratio of the maximum patch for forest land (P<0.05). (6) The plant diversity of each plant layer was also significantly affected by landscape patterns. The plant diversity in the herb layer presented a significantly negative correlation with the patch shape complexity of grassland and woodland, respectively (P<0.05). That in the shrub layer had a significantly negative correlation with landscape fragmentation degree of woodland and water, respectively (P<0.05). In the tree layer, a significantly negative correlation appeared between the plant diversity and the maximum patch index (P<0.05). The increase in the landscape fragmentation of parks may lead to the reduction of vegetation landscape area. It is suggested that the use of shrubs should be emphasized in the early stage of plant landscaping in parks, especially in some parks with relatively fragile ecological background, so as to improve the stability and low maintenance of plant communities. At the same time, a large area of core vegetation ecological patches should be preserved as much as possible to give better play to its ecological function. The research results provide a reference for the planning and designing of urban parks, the optimal allocation of plant communities, and the conservation of urban biodiversity.