A co-design process involving autistic children can provide a substantial benefit and optimal utilization of technologies to an off-the-shelf design-based one. Having a voice and making a contribution plays a major role in the co-design process. Yet autistic children exhibit varying communication and social skill and some of them may be minimally verbal or non-verbal. For these reasons, harmonizing the techniques of the co-design process with autistic children with varying characteristics requires detailed and careful consideration. To understand the techniques of the co-design process that accommodates all categories of autistic children, a systematic review of a co-design process involving autistic children was conducted, using six large databases (Scopus, ACM Digital Library, ScienceDirect, IEEE Xplore, SpringerLink, and Google Scholar). The search result includes 2482 papers of which only 82 met the inclusion criteria. The result of the data extraction analysis collection is classified according to techniques for accommodating autistic children of varying characteristics, the challenges encountered, and methods of minimizing those challenges. The review identifies four prominent themes within co-design research for autism: advances in co-design objectives and outcomes, participant recruitment determinants, core co-design methods, and the management of co-design challenges. Highlighting the need for inclusivity and equitable support, the study proposes recommendations for better integration of diverse communication abilities and multiple diagnoses in the co-design process, underlining the importance of adaptive technologies and methods to accommodate the needs of all children.