Using numerical simulation method based on finite-difference time-domain (FDTD), we study the characteristics of the multiple-core photonic crystal fibers (PCFs) in which square-nested compound lattices (SNCLs) with several defect regions are introduced. We find that each line defect in the PCFs can serve as a channel in wavelength division multiplexing (WDM) communication systems. The crosstalk can be suppressed because there is a band gap among each channel in the PCFs. And PCF amplifiers are expected to be used in the super-dense WDM systems.