This paper deals with establishing a transcriptional model in which the transcriptional activities of RNA Pol Ⅰ, Ⅱ, Ⅲ in intact nucleus could be determined separately in vitro. With modified Giuffrida method, the nuclei isolated from rat cerebral cortex were purified in good yields ranging from 41 to 52％ and high purity judging with phase-contrast microscopy. According to the method described by Blatti, RNA synthsis were studied under high or low (240 or 50 mmol/L (NH)₂SO₄) ionic strength condition. The inhibited and residual transcription in high-salt system and presence of α-amanitin represented the activities engaged by RNA Pol II and Poi III independently, ihe transcription in low-salt system containing α-amanitin was mainly responsible for RNA Pol I activities. In addition, some factors effecting on the nuclei transcription in vitro were also evaluated. It was concluded that the reported model had advantages being easy to operated, saving materials, and approching cell physiological conditions, it was suitable for studying transcriptional mechanism of cerebral cortex neurons.