Abstract: The changes of no-load expansion rate and load expansion rate in the new and old geotechnical test codes are compared and analyzed, and it is found that the calculation formulas of the two have changed significantly. Compared with the old code, the calculation results of the new code show that the expansion rate increases obviously, and the expansion amount increases accordingly, which will have a significant impact on engineering investigation, design and construction. A project is taken as an example. After the calculation of the new code, the total expansion of stratum has changed from 16.7mm to 51.8 mm, which has increased by about two times. The expansion and contraction grade of foundation soil has changed from Grade I to Grade II, and the design grade of foundation has changed from Grade C to Grade B. The foundation treatment measures and construction schemes have also changed accordingly. Therefore, engineers should consider this comprehensively and treat it rigorously.