This study explores the combination of magnetism and topology in two-dimensional alternmagnetic materials, introducing the concept of alternmagnetism, which is characterized by real-space antiferromagnetism and reciprocal-space anisotropic spin polarization. The authors use a four-band lattice model incorporating alternmagnetism and spin group symmetry to demonstrate the existence of type-I, type-II, and type-III bipolarized Weyl semimetals in alternmagnetic systems. They predict four ideal two-dimensional type-I alternmagnetic bipolarized Weyl semimetals: Fe$_2$WTe$_4$ and Fe$_2$MoZ$_4$ (Z=S,S,Te). The study also introduces the quantum crystal valley Hall effect, which can be achieved in Fe$_2$WTe$_4$, Fe$_2$MoS$_4$, and Fe$_2$MoTe$_4$ under spin-orbit coupling. These materials can transition from a quantum crystal valley Hall phase to a Chern insulator phase under strain. In contrast, Fe$_2$MoSe$_4$ remains a Weyl semimetal with only one pair of Weyl points. The position, polarization, and number of Weyl points in Fe$_2$WTe$_4$ and Fe$_2$MoZ$_4$ can be manipulated by adjusting the direction of the Néel vector, making them promising experimental platforms for investigating various alternmagnetic topological phases.This study explores the combination of magnetism and topology in two-dimensional alternmagnetic materials, introducing the concept of alternmagnetism, which is characterized by real-space antiferromagnetism and reciprocal-space anisotropic spin polarization. The authors use a four-band lattice model incorporating alternmagnetism and spin group symmetry to demonstrate the existence of type-I, type-II, and type-III bipolarized Weyl semimetals in alternmagnetic systems. They predict four ideal two-dimensional type-I alternmagnetic bipolarized Weyl semimetals: Fe$_2$WTe$_4$ and Fe$_2$MoZ$_4$ (Z=S,S,Te). The study also introduces the quantum crystal valley Hall effect, which can be achieved in Fe$_2$WTe$_4$, Fe$_2$MoS$_4$, and Fe$_2$MoTe$_4$ under spin-orbit coupling. These materials can transition from a quantum crystal valley Hall phase to a Chern insulator phase under strain. In contrast, Fe$_2$MoSe$_4$ remains a Weyl semimetal with only one pair of Weyl points. The position, polarization, and number of Weyl points in Fe$_2$WTe$_4$ and Fe$_2$MoZ$_4$ can be manipulated by adjusting the direction of the Néel vector, making them promising experimental platforms for investigating various alternmagnetic topological phases.