Based on the reading of Hui-hai's Gateway To The Sudden Enlightenment To Truth, this article considers some issues in the understanding of gateways to sudden enlightenment in the Southern Zen tradition. Regarding the relationship between Zen gateways to sudden enlightenment and the Buddhist classics, the article maintains that before Zen was divided into five sects, the Zen masters relied heavily upon the classics to interpret the ways of sudden enlightenment, and it was a mere fact that the classical doctrines were employed to clarify the sectarian motif, though not to perceive it. Down from Tsung-rni, much attention has been paid to the differences between Hong-zhou Sect led by Ma-zu Dao-yi and He-ze Sect led by Shen-xiu. But according to the writings of Hui-hai, they share more in common than ever acknowledged. Furthermore, many scholars of Zen thought tend to interpret the idea of entity of mind in Southern Zen tradition as a doctrine that mind alone is perpetual reality. But this article suggests, rather, that prominent Zen masters such as Hui-neng, Ma-zu Dao-yi, Hui-hai, Xi-yun of Huang-bo Temple, and those after the five sects, all hold to the position of emptiness of self-nature in Prajna and the middle way of eight negations in the Madhyamika.