The loss properties of air-core plastic photonic bandgap fibers are analyzed by multipole method. Despite the relatively large absorption loss of plastics (PMMA), the contribution of material absorption loss can be reduced significantly through appropriate selection of operating wavelength, number of cladding air-hole rings, radius of air-core, and position of photonic band gap. The transmission loss in this type of fiber can be decreased by an order of magnitude in comparison with that of conventional plastic optical fiber.