A nonwoven fabric having improved air permeability and strength is formed with a filament of sheath-core shape, the core part being constituted with blending a polyethylene terephthalate (PET) having melting point (Tm) of 250˜270° C. of 40 to 60 parts by weight with a polytrimethylene terephthalate (PTT) having melting point of 215˜235° C. of 10 to 50 parts by weight, the sheath part being constituted with a polyethylene terephthalate (PET) having melting point of 210˜230° C. of 10 to 30 parts by weight, and the core and sheath parts being spun with conjugate respectively, and formed with a web. The bicomponent nonwoven fabric uses a bicomponent polymer and improved spin method with conjugate and blending spinning to produce PTT nonwoven fabric having an improved strength and air permeability and soft property and proper resistance which are required for a variety of uses and to produce it economically.