  The transit timing variation (TTV) and transmission spectroscopy analyses of
the planet HAT-P-37b, which is a hot Jupiter orbiting an G-type star, were
performed. Nine new transit light curves are obtained and analysed together
with 21 published light curves from the literature. The updated physical
parameters of HAT-P-37b are presented. The TTV analyses show a possibility that
the system has an additional planet which induced the TTVs amplitude signal of
1.74 $\pm$ 0.17 minutes. If the body is located near the 1:2 mean motion
resonance orbit, the sinusoidal TTV signal could be caused by the gravitational
interaction of a sub-Earth mass planet with mass of 0.06 $M_\oplus$. From the
analysis of an upper mass limit for the second planet, the Saturn mass planet
with orbital period less than 6 days is excluded. The broad-band transmission
spectra of HAT-P-37b favours a cloudy atmospheric model with an outlier
spectrum in $B$-filter.
