We report the numerical simulation on the spiderlike photoelectron momentum distributions (PMDs) of a hydrogen atom ionized by a linearly polarized laser field using the semiclassical rescattering model (SRM) and the time-dependent Schr?dinger equation (TDSE), and focus on the extraction of scattering-amplitude phases. Based upon the previous research results, we draw a conclusion that the time parameters obtained from the SRM and the saddle-point theories are approximately equal. In addition, we propose a novel method for phase extraction. Moreover, we establish two first-order approximate formulas to analytically describe the scattering amplitude phase. The phase obtained by the proposed method is related to the longitudinal and transverse momenta. The new method obviously enhances the extracting precision, although it increases the computation load.