In a preceding article [the author, ibid. 4, 825-831 (1983; Zbl 0557.76118)], the relation between thermodynamics condition and inceptive cavitation stage has been discussed. In this paper, we try to introduce the volume function of inceptive cavitation bubbles, \(z_ 0(r)\), instead of the energy equation used in the preceding article, for discussing the cavitation similarity problem in similar flow systems. Under this condition, theoretical results show that the inception cavitation number \(K_ i\) increases with a rise of geometry linear scale. In other words, if two flow systems are kept with similar pattern and liquid, it is impossible to satisfy the cavitation similarity. This conclusion is in accordance with practical results.