To assess the environmental factors determining the zonation between Phacelurus latifoliusand Phragmites australis, vegetation survey and soil analysis were performed at a tidal marsh. The vegetation of the tidal marsh was classified into P. latifoliusand Suaeda japonicadominated quadrats, P. latifoliusand P. australisdominated quadrats, P. australisdominated quadrats, and P. australisand other land plants dominated quadrats. The density of P. latifolius(83.7 ± 5.5 shoots m−2) was higher than that of P. australis(79.3 ± 12.1 shoots m−2) in each dominated quadrat but height of two species were similar. Soil environmental characteristics of P. latifoliusdominated quadrats appeared to be affected by tide based on higher soil electric conductivity (ECPL= 1530 ± 152 μS cm−1; ECPA + PL= 689 ± 578 μS cm−1; ECPA= 689 ± 578 μS cm−1) and lower pH (pHPL= 5.96 ± 0.16; pHPA + PL= 6.28 ± 0.31; pHPA= 6.38 ± 0.22). In redundancy analysis, environmental characteristics of P. latifoliusdominated quadrats and P. australisdominated quadrats were clearly separated and those of P. latifoliusand P. australisco-dominated quadrats were similar to P. australisdominated quadrats. From our investigation, P. latifoliusshowed relatively high competitiveness when compared to P. australisin lower tidal zone rather than upper tidal zone. Zonation of P. latifoliusand P. australisseems to be a transitional zone between halophytes and land plant species.