The invention relates to a method for optimizing an optimal forgeable temperature range by using SICO. The method is characterized in that a sample is installed in the vacuum chamber of a testing machine; two ends of the sample are clamped with fixtures; the parameters of deformation process are set in programming; a resistance heating method is employed for heating to a deformation temperature under a high vacuum condition; then compression is axially applied onto the sample; cracks occur on the surface of the sample when strain reaches a certain extent; analysis and calculation are carried out according to data acquired in experiments, and a circumferential stress-circumferential strain curve and a relation curve of strain and deformation temperature needed in surface cracking are drawn; and then the forgeable temperature range is optimized. The method provided by the invention overcomes the disadvantage of a wide high-temperature thermoplastic temperature range, improves the yield of forging, reduces the failure rate of forging and has great significance to prevention and pre-judgment of hot-working cracks.