Abstract: Four sediment cores, collected in Yangpu Harbour on Hainan Island,were analyzed for textural parameters and Pb- 210, Cs-137 activities,Yangpu Harbour is tidally flushed and has sediment distribution pattern which is related primarily to the tidal current pattern. Sandy(fine and coarse sllty sand ) material is distributed along the tracts of relatively high speed tidal currents underlying the shallower regions of the harbour while finer-grained,silty muds tend to accumulate in the deeper parts of the tidal channel itself. Measurements of textural paramenters have indicated that sedimentation is episodic in many sections of the harbour with successive cycles of particle erosion and deposition leading to the variable accumulation of material,particularly in the tidal channel. Because of complex stratigraphy of interbedded layers of sand and mud,Pb-210 profiles in Yangpu Harbour reveal abnormal distributions. Since the Pb-210 activity was almost exclusively associated with the finegrained,clay,component of the sediment load,the nomalization of these data to the%clay content of the sediment permitted the determination of depositional rates,despite instances of variability in the Pb- 210 activities. The distributions of Cs- 137 in two cores were measured,both the position of the horizon (corresponding to the first appearance of Cs-137 in the environment )and the peak (corresponding to the period of maximum deposition ) have been used to determine sedimentation rates. Rates based on the position of peak of Cs- 137 profile are in good agreement with that based on Pb-210 dating,and rates based on the occurrence of the horizon are slightly larger than that based on Pb-210 dating. Sedimentation rates,determined using P1i-210 and Cs-137 dating methods,were 0. 5-2cm/y in the sediments underlying the tidal channel,and were 1~2cm/y in the sediments on the swash platform area("block gate shoal") during past 100 years.