The invention discloses silicon rubber and a preparation method thereof, and phenolic aldehyde modified silicon rubber resin and a preparation method thereof. A structural formula of the silicon rubber is as shown in the description, wherein x is equal to 70-80, and y is equal to 10-20. A structural formula of the phenolic aldehyde modified silicon rubber resin is as shown in the description, wherein n, x, and y are degrees of polymerization, n is equal to 10-20, x is equal to 70-80, and y is equal to 10-20. The preparation method for the phenolic aldehyde modified silicon rubber resin comprises the following steps: adding 90-110 parts by mass of brominated phenolic resin and 180-220 parts by mass of an organic solvent into 100 parts by mass of silicon rubber, reacting for 24-48 hours in 70-80 DEG C, until solution is clarified and transparent; and adding 9-11 parts by mass of an end sealing agent, continuously reacting for 4-5 hours, to obtain reacting liquid containing the phenolic aldehyde modified silicon rubber resin. The prepared phenolic aldehyde modified silicon rubber resin is capable of solving a problem in a traditional silicon rubber ablation process that pulverizationis easily generated, and has a higher mechanical property at the same time.