A fundamental 1 \times 2 beam splitter based on the self-imaging phenomena in multi-mode one-dimensional (1D) photonic crystal (PC) waveguides is presented, and its transmission characteristics are investigated using the finite-difference time-domain method. Calculated results indicate that a high transmittance (>95%) can be observed within a wide frequency band for the 1 \times 2 beam splitter without complicated structural optimizations. In this letter, a simple and compact 1 \times 4 beam splitter is constructed by combining the fundamental 1 \times 2 beam splitter with the flexible bends of 1D PC waveguides. Such beam splitters can be applied to highly dense photonic integrated circuits.