We developed a transistor mixer with broadband(100～300MHz). It has not only a mixing gain characteristic of transistor mixer，but also a linear dynamic range approximato to that of the diode. Therefore，it is better solved that the contradiction between the mixing gain and the 1inear dynamic range. However，it is often difficult to explain these characteristics by "The Mixing Transconductance Theory". To overcome these difficueties we try to use "The Mixing Admittance-Linear Gain" Model to expllain these ones so that we easily analyse the testing curve and data of transistor mixers，and proved fundamental agreement of both the model analysis and the practice test.