The purpose of this paper is to explore the current situation and challenges of assessing science learning achievement in primary school. We interviewed 23 primary school science teachers from 17 schools in an East metropolitan area of 10 million people in China. Drawing from a grounded theory study, our findings revealed a generally favorable disposition among primary school science teachers toward the assessment on scientific academic performance. But the current primary school science assessment is still lacking in standardization. Considering assessment methods, paper-based test method is the most commonly used in primary school science academic assessment, and is also considered to be the most effective method. The current academic assessment method is mainly based on teacher assessment and supplemented by student assessment. Assessment on science academic performance also faced several challenges, including undiversified assessment methods, a heavy workload for teachers and students, a lack of financial support and a lack of assessment instruments.