There exists an evident turning point in the duration curve of penetration resistance versus time in the setting process of roller compacted concrete(RCC) in layer construction, and it coincides with the initial setting time of concret. A mathematical model representing mutal relations is estabished through studying the influences of surrounding temperature, relative humidity and wind velocity on RCC initial setting time and its appropriate penetration resistance. and a quick judgement method on setting state of RCC in construction site is proposed. Application and inspection on three RCC projects using the suggested method are described and concluded that the method can grarantee the adherence quality between concrete layers.