  We present the compact radio structure of three radio-loud narrow line
Seyfert 1 galaxies from VLBA archive data at 2.3, 5 and 8.4 GHz. In RXS
J16290+4007, the radio structure is mostly unresolved. The combination of
compact radio structure, high brightness temperature and inverted spectrum
between simultaneous 2.3 and 8.4 GHz, strongly favors jet relativistic beaming.
Combining with the VLBI data at 1.6 and 8.4 GHz from literatures, we argued
that RXS J16333+4718 may also harbor a relativistic jet, with resolved core-jet
structure in 5 GHz. B3 1702+457 is clearly resolved with well defined jet
component. The overall radio steep spectrum indicates that B3 1702+457 is
likely a source optically defined as NLS1 with radio definition of compact
steep spectrum sources. From these three sources, we found that radio loud
NLS1s can be either intrinsically radio loud (e.g. B3 1702+457), or apparently
radio loud due to jet beaming effect (e.g. RXS J16290+4007 and RXS
J16333+4718).
