The problem of doctoral students’ delayed graduation has been widely concerned by the academic circles and the society. Based on the insiders-outsiders perspective, by attribution analysis， through analysis of the current situation, causes and essence of the delayed completion of doctoral studies in architecture, it is found that whether doctoral students in architecture can graduate on schedule is affected by five dimensions, such as individual, tutor, team, discipline and system. Difficulty in transforming perceptual design thinking into rational logical thinking, imbalance of the dual identity of designers and researchers, the mismatch of the mentoring model with the needs of modern scientific research, the mismatch between knowledge method and evaluation system, and the improper training mechanism and assessment mechanism are the root causes. In order to provide a useful reference for improving the training mode of doctoral students in architecture and reducing the delay rate, this paper puts forward some measures, such as adjusting the basic academic years of doctoral students, implementing a diversified evaluation system, expanding the scale of integrated graduate education, constructing the academic research echelon, optimizing the evaluation system of tutors, and establishing the academic assistance mechanism.