In order to accurately study the chemical shrinkage performance of polymer cementing materials, a double-tube chemical shrinkage testing device without rubber stoppers was developed. Digital image technology was adopted to continuously monitor and count it, which solved the problem of large test errors caused by manual reading and the internal stress of the rubber stoppers in the original device. The results show that the coefficient of variation of the geopolymer chemical shrinkage values measured by this method is 11% (maximum value) and 22% (stable value) of the traditional method (ASTM-C1608), and the degree of data dispersion is 18.4% of that of the traditional method. It is indicated that the test results obtained by adopting this method are more accurate. The total chemical shrinkage of geopolymer cementitious materials under different oxide molar ratios was measured and analyzed by this method, and the influence of the oxide molar ratio on the chemical shrinkage rate was calculated. Finally, the mathematical equations of the oxide molar ratio and the peak and peak rate of geopolymer chemical shrinkage were given. It provides a new method for the study of the early cracking behavior of geopolymers and their reaction kinetics.