We present our optical photometric and spectroscopical observations of GRB 140629A .
A redshift of z = 2.275 \pm 0.043 is measured through the metal absorption lines in our spectroscopic data .
Using our photometric data and multiple observational data observed with other telescopes , we show that its optical light curve is well interpreted with the standard forward shock models in the thin shell case .
Its optical-X-ray afterglow spectrum is jointly fitted with a single power-law function , yielding a photon index of -1.90 \pm 0.05 .
The optical extinction and neutral hydrogen absorption of the GRB host galaxy are negligible .
The fit to the light curve with the standard models shows that the ambient density is 60 \pm 9 cm ^ { -3 } and the GRB radiating efficiency is as low as \sim 0.24 \% , likely indicating a baryonic-dominated ejecta of this GRB .
This burst agrees well with the L _ { p,iso } - E _ { p } ^ { { } ^ { \prime } } - \Gamma _ { 0 } relation , but confidently violates those empirical relations involving geometric corrections ( or jet break time ) .
This gives rise to an issue of possible selection effect on these relations since the jet opening angle of this GRB is extremely narrow ( 0.04 rad ) .