The intended curriculum is arguably one of the most important components within any national educational system although those in primary science have not been subject to extensive research scrutiny. Based on reformed primary science curricula from Hong Kong, mainland China, and Taiwan, we compared them on two key features: (1) levels of knowledge and cognitive processes from their learning outcomes; and (2) coherency of topics that influence the ease, meaningfulness, and quality of learning in the subject. In the former, we coded their intellectual demands (i.e., what learners must know and do) using revised Bloom's taxonomy while for the latter, we investigated the coverage, focus, sequence, and emphasis of topics across grades. We found that curricula from Hong Kong and mainland China generally focused on the first two levels of knowledge domains and cognitive processes while Taiwanese learning outcomes were predominantly coded as Apply. Different aspects of coherency in the intended curriculum revealed which topics were covered, their focus, and sequencing across grade divisions as well as their emphasis of topics. Our empirical research therefore adds to the small number of comparative studies in primary science curricula. It can also practically assist policy- and curriculum-making in these regions as they seek to understand and develop quality curricula in primary science.