An organic semiconductor crystalline film and weak oriented epitaxy growth preparation method thereof. The organic semiconductor crystalline film is a n-type semiconductor or a p-type semiconductor, and organic semiconductor crystal molecules in the organic semiconductor crystalline film are oriented in a stand-up manner on the ordered substrate, and have an oriented relationship with the ordered substrate. The organic semiconductor crystalline film prepared by the present invention is useful for organic transistor and organic phototransistor devices. The method of the present invention can control the high carrier mobility direction of organic semiconductor crystals to have ordered orientation in the film, enhance contacts between crystals, improve mechanical strength and micro-machining property of the film, and give a high carrier mobility. The carrier mobility of weak oriented epitaxially grown film of the present invention is 0.32 cm2/Vs, which is 5 times as large as that of a vapor phase deposited film, and is similar to that of single crystal. The present invention is adapted to glass substrates and plastic substrates.