The specific heat ratio of air is the key parameter in describing the hypersonic flow field. The existing search tables of its values indexed by temperature and air pressure are not suitable for hypersonic flow field calculation. Therefore, theoretical calculations of the hypersonic flow field set the specific heat ratio of air at a constant value resulting in large calculation errors in general. In this paper, a 2-D search table for the specific heat ratio of air based on velocity and height as search variables is proposed for hypersonic flow field calculations to replace the invalid temperature-pressure specific heat ratio of air. Taking the calculation of the stagnation temperature of the hypersonic flow field as an example, the theoretical calculation results and the measured data of the RAM-C hypersonic flight experiment are compared and discussed. A comparison of results shows that the proposed 2-D search table meets the computational requirements for hypersonic flow field calculations and provides a fast and accurate query database for the specific heat ratio of air and related parameters.