The literature on the formation of the solar silicon spectrum and on its application to the solar atmosphere diagnostics is reviewed. Particular attention is given to studies on the determination of the solar silicon abundance. A reliable estimate for this abundance is of critical importance for the solution of the solar metallicity problem. We discuss the errors of oscillator strengths, broadening damping constant and rates of inelastic collisions with hydrogen atoms which cause some errors in estimates of the silicon abundance. We summarize the investigations relative to the impact of some deviation from local thermodynamical equilibrium, inhomogeneous structure of the solar atmosphere and small-scale magnetic fields on the formation of solar Si I lines.