Abstract: Radio frequency (RF) phase reference line is one of key components in particle accelerator, which can provide phase locked RF reference signal to low-level RF (LLRF) system, beam diagnostic system, timing system or other phase sensitive systems. To reduce phase fluctuations caused by ambient temperature changes in long-distance particle accelerators, phase reference system has been implemented in several accelerator plants. In current phase reference line (PRL) projects, thermal-control based and fibre phase-locked based are mainly implementation methods. Compared with these PRL solutions, the RF phase averaging method has been proven to be able to maintain phase stability between long-distance nodes and it is easier to be applied to installation and maintenance in situ. The method of using phase-locked loop (PLL) phase averaging PRL still has some limitation on nodes quantities. For considering of simplify structure and more nodes can be added and also decreasing requirements for devices, it is necessary to evaluate the phase averaging structure without PLL. The results for the single-end input and the dual-end input structure of non-PLL design show that both structures have the similar accuracy at 0.1° ~ 0.3°, and the results show that the possible reasons of phase instability in different implementation structures, besides ambient temperature, also has the material of coaxial cable, combination phase, imbalanced combination, etc.