W50 is the large Galactic radio nebula associated with the microquasar jets SS433. However, the formation mechanism of the W50/SS433 complex has long been a mystery. We investigate a new scenario in which the SS 433 jets themselves form the W50/SS 433 system using the magnetohydrodynamics simulations (Ohmura et al. 2021). The morphology of the radio nebula is spheroidal at early times; afterward, the shell and wings are developed by the broadening spherical cocoon. As a result, jets can produce shell and wing morphology like W50 nebula with a realistic age of SS433. We also find that most of the kinetic energy is dissipated at the oblique shock formed by the interaction between backflow and jet beam flow, rather than at the jet terminal shock.