Cruciform compound, 2,6-bis(phenylethynyl)-4,8-bis(phenylethynyl)benzo[1,2-b:4,5-b']dithiophene and its alkyl substituted derivatives, 1a-d, were designed and synthesized. Their physicochemical properties were studied by thermogravimetric analysis, absorption spectra, and cyclic voltammetry. Single crystal diffraction results revealed that 1a-d adopted different molecular packing in the solid state, which was caused by the introduction and the different orientations of alkyl chains. The single micrometer ribbon transistors of 1a displayed high mobility up to 0.81 cm(2) V(-1) s(-1). And the as-spun thin film transistors of 1c exhibited mobility as high as 0.106 cm(2) V(-1) s(-1), 2 orders of magnitude higher than those of 1b (0.006 cm(2) V(-1) s(-1)) and 1d (0.002 cm(2) V(-1) s(-1)).