On the basic of bipartite networks，bielemental networks are defined as networks which include two kinds of vertexes，and connections between different kinds of vertexes are permitted. In this article，a bielemental random network model is founded，and the structure of the bielemental random network is studied. Small-world effect can be found in such model，furthermore，the average shortest path length is smaller than that of unipartite random networks. And the proportion of the numbers of two kinds of vertexes is a very important factor.