With the exacerbation of aging in China, the problem of nursing for the elderly has increasingly become one of the focuses of social concerns. Because of the popularization of mobile devices, using mobile devices to assist the care of the elderly has become a feasible solution. In this paper, we developed an elderly life assistant system (ELAS) based on mobile devices, which includes two apps (applications), i.e., the Supporter side and the Elderly side. The Supporter side helps the supporters to care for the elderly, remotely helps the elderly to input the drug information and record medication; the Elderly side assists the daily lives of the elderly. The main functions of the system are medication reminding, reading assistance, navigation route assistance and adaptive voice navigation (AVN), in which AVN can automatically adjust the volume of navigation according to external noise, providing better navigation effect for the elderly. Experiments show that ELAS is helpful to the elderly in daily life, and improves the ability of the elderly to take care of themselves.