Valley pseudospin in monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Mo</mml:mi><mml:msub><mml:mi>Si</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Mo</mml:mi><mml:msub><mml:mi>Si</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:…

For a long time, two-dimensional (2D) hexagonal ${\mathrm{MoS}}_{2}$ was proposed as promising material for the valleytronic system. However, limited size of growth and low carrier mobility in restrict its further application. Very recently, new kind 2D MXene, $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{N}}_{4}$, successfully synthesized with large size, excellent ambient stability, considerable hole mobility. In this paper, based on first-principles calculations, we predict that valley-contrasting properties can be realized monolayer $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ derivative $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{As}}_{4}$. Beyond traditional two-level valleys, valleys $\mathrm{Mo}{\mathrm{Si}}_{2}{\mathrm{As}}_{4}$ are multiple folded, implying another valley dimension. Such multiple-folded described by three-band low-power Hamiltonian. This study presents theoretical advance potential applications devices, especially information processing.