The invention relates to a pig pseudorabies virus natural low-virulent C strain and a heatproof preservation method thereof. The microbe collection registry number of the strain is CCTCC NO: V201114. According to the invention, various cryoprotectant substrates are mixed and blended according to a certain ratio; the cryoprotectants are respectively subject to aseptic processing; cryoprotectant components that can be subject to high-pressure sterilization are dissolved in bi-distilled water, and are sterilized for 15-30min under a temperature of 108-121 DEG C; cryoprotectant components that can not be subject to high-pressure sterilization are dissolved in bi-distilled water according to a certain formula, and are sterilized by using a filter membrane with a size of 0.22mum; all the cryoprotectant components are then mixed into a heatproof cryoprotectant; the heatproof cryoprotectant is mixed with a pseudorabies virus liquid according to a ratio of 1:1-1.2; and the mixture is lyophilized with a corresponding lyophilization curve. Compared to prior arts, the C strain provided by the invention has good stability. In a fifth generation animal of continuous back-procreation, the genetic sequence is stable, and no mutation is found. Therefore, the strain provided by the invention provides a good resource for the researches of pig pseudorabies low-virulent vaccines. The strain can bepreserved for 24 months under a temperature of 2-8 DEG C, and the virus titer is reduced by no more than 1 titer.