The miniature construction of the microstrip triplexer representing the planar microstrip structure containing junction of the microstrip star lines and three band passing filters each of which is probed on the operating frequency, is researched. Formation of bandpass range in each of channels provides the rectangular spiral resonator which length equals to wavelength in the line. Also results of numerical modeling of filters which are set up on frequency 1; 1,125 and 1,25 GHz, respectively, are given. As material of a substrate FR-4 with dielectric permittivity ε=4,4 and 1,5 mm thick appears. The offered construction has small overall dimensions, small entered losses and low cost of manufacture.