LaNi5 is a commercial hydrogen storage alloy with great potential. But its performance still needs to be optimized to meet the standard proposed by the US Department of Energy. Element substitution is a very important method to optimize the performance of hydrogen storage alloys, especially suitable for AB5 alloys. As a novel method to produce nanocrystalline hydrogen storage alloys, mechanical alloying is also often applied to optimize the properties of hydrogen storage alloys. In this work, first of all, the simulation method based on first principles is applied to predict the performance of 8 elements substituting Ni respectively, and select the most suitable element to substitute Ni. Then the phase composition characterization, hydrogen storage performance tests and electrochemical performance tests were carried out. It was found that mechanical alloying can greatly improve the hydrogen storage performance of LaNi5, and different ball milling times can bring about different performance changes. After adding Cr to the ballmilled LaNi5, the properties of the formed LaNi4Cr were further improved.