  Aims. The X-ray luminous and radio-loud AGN SRGE J170245.3+130104 discovered
at z $\sim$ 5.5 provides unique chances to probe the SMBH growth and evolution
with powerful jets in the early Universe. Methods. We present 1.35 - 5.1 GHz
Very Long Baseline Array (VLBA) results on the radio continuum emission and
spectrum analysis for this quasar in a low flux density state. Results. This
source is unresolved at three frequencies with the total flux densities of
8.35$\pm$0.09 mJy beam-1, 7.47$\pm$0.08 mJy beam-1, and 6.57$\pm$0.02 mJy
beam-1 at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the
brightness temperature is higher than 109 K. Conclusions. Compared with
previous radio observations with arcsec-scale resolution, nearly all the radio
emission from this source concentrates in the very central milli-arcsecond
(mas) scale area. We confirm this source is a bright blazar at z > 5. This
young AGN provide us the great chances to understand the first generation of
strong jets in the early Universe.
