Asymmetric line shape of states is a distinguished characteristic which is often encountered when thresholds and states interacts. Fifty years ago, Fano[1] that the interaction of bare states with one or several thresholds of continua would give rise to special asymmetric peaks of the corresponding resonances, which is a common interference phenomenon in quantum physics. It is more obvious for sharp resonances, e:g:, heavy quarkonium states, because their widths are smaller by orders of magnitudes than their masses. The (3770) state is narrow with a width of around 30 MeV and locates about 35 MeV above the D￣D threshold. It is ideal to investigate how this threshold effect influences the properties of states.
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