The generalized-master-cquation(GME) theory of excitation transfer and optical spectra were adopted to investigate the time characteristics of sxciton coherent transport in the molecular aggregates of identical and different chlorophylls for the first time. A coherent time of 200 fs was derived based on its memory function calculation for the transport be-tween chlorophyll a and chlorophyll b

and the results for chlorophyll a and chlorophyll b in solution were 350 fs and 160 fs

respectively. The exciton coherent transport in above aggregates is analysed to be a transfer before vibrational relaxation process. The effects of coherence on excitation transfer and some major factors affecting coherent time are also discussed.