In this paper, the influence of charge trapping memory storage feature is studied by doping the substitutional impurity Al and introducing oxygen vacancy within HfO2. HfO2 is widely used in trapping layer of charge trapping memory, for it belongs to high dielectric constant materials with the abilities to shrink the device size and improve the device performance. Materials studio and Vienna Ab-initio Simulation Package are used to investigate the influence of doping Al on the formation of the oxygen vacancy in HfO2 as a trapping layer. At the same time, the interaction energy of two defects at different distances is calculated. Results show that doping the substitutional impurity Al reduces the formation energy of oxygen vacancies in HfO2, and the reduced formation energy of the three-fold-coordinated O vacancy is larger than that of the four-fold-coordinated O vacancy. After having studied three different defect distances between the substitutional impurity Al and the three-fold-coordinated O vacancy, the results indicate that the system acquires the largest charge trapping energy, the most of quantum states, the smallest population number, and the longest Al–O bond length when the distance between the defects is 2.107 Å. Studying the bond length changes of the three systems after writing a hole, we obtain a result that the change of Al–O bond length is the smallest when the distance between defects is 2.107 Å. In conclusion, the data retention in the trapping layer of monoclinic HfO2 can be improved by doping the substitutional impurity Al. This work will provide a theoretical guidance for the performance improvement in the data retention of charge trapping memory.