  We fit the most updated broadband spectral energy distribution from radio to
X-rays for NGC 4258 with a coupled accretion-jet model that surrounding a Kerr
black hole (BH), where both the jet and the warped H_2O maser disk are assumed
to be triggered by a spinning BH through Blandford-Znajek mechanism and
Bardeen-Petterson effect respectively. The accretion flow consists with an
inner radiatively inefficient accretion flow (RIAF) and an outer truncated
standard thin disk, where the transition radius R_tr~3*10^3Rg for NGC 4258
based on the width and variability of its narrow Fe K$\alpha$ line. The hybrid
jet formation model, as a variant of Blandford-Znajek model, is used to model
the jet power. Therefore, we can estimate the accretion rate and BH spin
through the two observed quantities--X-ray emission and jet power, where the
observed jet power is estimated from the low-frequency radio emission. Through
this method, we find that the BH of NGC 4258 should be mildly spinning with
dimensionless spin parameter a_*=0.7\pm0.2. The outer thin disk mainly radiates
at near infrared waveband and the jet contributes predominantly at radio
waveband. Using above estimated BH spin and the inferred accretion rate at the
region of the maser disk based on the physical existence of the H_2 O maser, we
find that the warp radius is ~8.6*10^4 R_g if it is driven by the
Bardeen-Petterson effect, which is consistent with the observational result
very well.
