Distinct diurnal variation of precipitation around the Strait of Malacca was elucidated using TRMM rainfall data and MM5 model. TRMM rainfall data shows the contrast of sea and land surface diurnal rainfall, in early-morning and evening, respectively. The model study in typical season suggests the following mechanism of the diurnal precipitation system. 1) During daytime, deep convection are induced by convergence of the up-slope winds caused by solar radiative heating over the mountains, while divergence is clear above the strait. This convection should produce an evening rainfall. 2) In evening, when daytime convections declines along mountains both side of the strait, cold air mass caused by evaporation of raindrop begins to blow toward the strait in lower atmosphere. This cold flow transports lower water vapor to the strait associating with a down-slope wind. 3) In midnight, two cold moist air flows converge above the strait, making a precipitation along the strait. The shape of terrain, like a deep basin, should strengthen the convergence in a layer below 900hPa along the strait.