Abstract: Wave functions of helium atom and hydrogen molecule in momentum space have been derived. For helium atom, dynamic variables P_r,P_θ, and P_φ,which are conjugated with position variables r,θ, and φ respectively, are used; while for hydrogen molecule, dynamic variables P_ζ,P_η, and P_φ, which are conjugated with position variableζ,η, and φ respectively, are used.