The invention provides a high carbon high silicon martensite stainless steel billet. The steel billet is characterized by comprising the following components by weight percent: 0.41-0.47% of C, 2.80-3.20% of Si, 0.50-0.80% of Mn, 8.50-9.20% of Cr, 0.30% or less of Ni, 0.028% or less of P, 0.005% or less of S, 0.20% or less of W, 0.20% or less of Mo, 0.15% or less of V, 0.015% or less of Nb, 0.015% or less of Ti, 0.010% or less of Al and the balance Fe and inevitable impurities. The invention also provides a preparation method of the high carbon high silicon martensite stainless steel billet. The method comprises the following steps: performing primary smelting with an electric arc furnace (EAF), performing argon-oxygen decarburization (AOD) smelting, refining with a low frequency (LF) furnace, performing continuous casting, annealing and rolling. The method of the invention has simple operation, can stably control the quality of the continuous casting billet, completely suppresse cracks, overcome the defect of concentration of stress and increase the casting yield and quality stability of the martensite stainless steel.