The `Samyuktagama` talks more about anattan and less about `sunna`. Already traceable in the sutta and `vyakarana` of `Samyuktagama` were the very profound meanings of `sunna` and `sunnatanupassana` such as the `paticcasamuppanna` dharmma of aging, death, etc.，the `mahasunnata` of anatta and anattaniya, the `paramatth- asunna` of having kamma and retribution but no doer，the `sunna` loka, the `sunnata-(ceto) samadhi` of no permanence, ever-lasting，non-changing dhamma, `atman` and `mama-kara`，the "`Acariya` dhamma `mudda nanadassana-visuddhi` "of `sunnata`，animitta, akincana, nirodha `pahana-parinna`，etc. However, "The holy disciples reside in `anatta-sanna`, achieve abolishment of `asmimana` and realize `nibbana` "is still the main stream of `muttigami` magga. Due to the scope of anattan is very deep, very wide，difficult to understand and difficult to realize，the method of arriving no "`ahamkara`, `mamamkara` and `mananusaya` "through the practice of "`sunnatasamadhi` "and "`sunnatanupassana` " is developed and expounded in `Majjhimagama` and `Ekottarikagama` later.
The `Ekottarikagama` transmitted by the Terminal School of `Mahasanghika` retains the trace of the evolution of "replacing anattan with `sunna` ". Based on it，this paper investigates why and how the `Ekottarikagama` used `sunna` to replace anattan. Because of the difference of audience，the `Samyuktagama` of early Buddhism referred to anattan as "not a soul" in one time and "without a soul" in another time. However，due to the different viewpoints of modern scholars, there arouses a debate of interpreting "anattan of panca `khanda` " as "not a soul of panca khanda" or "without a soul of panca `khanda` ". Such disputation has never been found in `Ekottarikagama` which uses `sunna` to replace anattan.
The `Samyuktagama` points out that `sunnata-samadhi`，`animitta-samadhi` and akincana are `nana'ttha nana- vyanjana` or `eka'ttha vyanjanam nanam`，but it explains only briefly. The understanding of such `'ttha` and `vyanjana`，the carrying out of `sunnatanupassana`，the realization of the meaning of `sunna` and the experience of the greed，hatred and delusion `sunna` are very important. This paper has a supplementary explanation on such tayo `samadhi/tisso cetovimutti` and other relevant items.
The `sunnata-vihara` of `Samyuktagama` and `Majjhimagama` describe how to lead daily life by being connected with `sunnata`，and how to do the devotation of solitude meditation with the application of `sunnatanupassana` so as to practice `yathabhucca`， `sunnatavakkam`，avipallattha, `asavanam` khayo，`anasava`，`asamkhata` and ceto-vimutti.
