Puts forward a kind of economical and practical pulse transformer with closed magnetic core type, to improve the original pulse transformer, in order to improve the coupling coefficient and decrease the leakage inductance, thus reducing the rising time of output pulse voltage. Using electromagnetic induction principle to analyze and test, to improve the original pulse transformer in adding a reverse parallel auxiliary winding to connect the primary and secondary windings, to study the coupling and the output characteristics of pulse transformer, to take measurement and calculation of the important parameters. The pulse signal of the test is square wave pulse of the duty ratio 5%, the frequency 10 kHz, the rising time of the pulse transformer output pulse voltage of with the auxiliary winding than the with no auxiliary winding less 200 ns, the experimental results verify the rationality of design.