Abstract: A low specific gravity thermosetting resin composition of high fluidization with excellent mechanical properties, and methods for preparing the same, wherein a thermosetting resin composition for outer plastic panel of an automobile is modified in that a part of the inorganic filler is replaced with a low specific gravity filler, and the type of a filler and a thickener are altered from those compounds normally used for car panels. The are light-weight. The process prevents the degradation of the low specific gravity filler which can normally occur under a general compacting pressure. The composition has superior plasticity even when press forming under a low pressure.