Individuals with Autism Spectrum Disorder (ASD) can face great challenges in learning and maintaining basic living skills. This not only reduces their possibilities of independent living and employment, but also continuously brings social and financial burdens to their caregivers/mentors. Although research has been proposed to help autism users, most of them focus on improving social and communication skills or providing help for emergency situations. In this paper, we propose a novel portable context-aware assistive system to help autism users in their daily activities such as cooking and cleaning. To make it easily accessible and cost effective, we employ mobile devices and cheap context sensors. Our care system has been implemented and tested under different settings, and a user study involving ten pairs of autism users and their caregiver/mentors has been carried out to evaluate our approach. User feedback is highly positive.