Driven by the shortage of qualified nurses and the increasing average age of the population, the ambient assisted living style using intelligent service robots and smart home systems has become an excellent choice to free up caregiver time and energy and provide users with a sense of independence. However, users’ unique environments and differences in abilities to express themselves through different interaction modalities make intention recognition and interaction between user and service system very difficult, limiting the use of these new nursing technologies. This paper presents a multimodal domestic service robot interaction system and proposes a multimodal fusion algorithm for intention recognition to deal with these problems. The impacts of short-term and long-term changes were taken into account. Implemented interaction modalities include touch, voice, myoelectricity gesture, visual gesture, and haptics. Users could freely choose one or more modalities through which to express themselves. Virtual games and virtual activities of independent living were designed for pre-training and evaluating users’ abilities to use different interaction modalities in their unique environments. A domestic service robot interaction system was built, on which a set of experiments were carried out to test the system’s stability and intention recognition ability in different scenarios. The experiment results show that the system is stable and effective and can adapt to different scenarios. In addition, the intention recognition rate in the experiments was 93.62%. Older adults could master the system quickly and use it to provide some assistance for their independent living.