In the design of automotive digital cockpit, it is an important basis for improving the design level of the cockpit by obtaining the subjective data of users with accuracy and reliability. The subjective measurement method with its scale as tools is commonly used, which is irreplaceable and has a wide application. However, this method has the disadvantages of low reliability and inaccurate aggregation when the sample size is small. The fuzzy set theory was taken to construct a fuzzy scale to avoid the information loss during the rating, so that the measurement could be much closer to people's real subjective opinions. Meanwhile, a linear feedback iterative algorithm was used to optimize the weight allocation, so that the individual opinions in a small sample size and their aggregated opinions could overlap to the greatest extent. As a result, a systematic method for constructing a fuzzy scale was obtained, which improved the reliability of subjective measurement. A maximum agreement method was proposed, which improved the accuracy of subjective measurement aggregation. The optimization of subjective measurement method provides a new way for improving the design of automotive digital cockpit.