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In this paper, we study the photon-photon pair production optical depth for10 GeV--1 TeV gamma rays from 3C 279 due to the diffuse radiation of broad-lineregion (BLR). Assuming a power-law spectrum of $E_{\gamma}^{-a_2}$ for thephoton intensity of very high energy (VHE) gamma rays, $a_1 \gtrsim 405$ and$a_2\gtrsim 6.4$ are inferred by the integrated photon fluxes measured by MAGICand HESS. Based on this power-law spectrum, the pre-absorbed spectra areinferred by correcting the photon-photon absorption on the diffuse photons ofthe BLR (internal absorption) and the extragalactic background light (externalabsorption). Position of gamma-ray emitting region $R_{\rm{\gamma}}$ determinesthe relative contributions of this two diffuse radiation to the totalabsorption for 10 GeV--1 TeV gamma rays. The internal absorption could makespectral shape of gamma rays more complex than only corrected for the externalabsorption, and could lead to the formation of arbitrary softening andhardening gamma-ray spectra. It should be necessary for the internal absorptionto be considered in studying 10 GeV--1 TeV gamma rays from powerful blazars.The energies of annihilated gamma-ray photons due to the internal absorptionare likely to be mainly reradiated around GeV. Our results indicate that$R_{\rm{\gamma}}$ may be between the inner and outer radii of the BLR for 3C279. This implies for powerful blazars that $R_{\rm{\gamma}}$ might be neitherinside the BLR cavity nor outside the BLR, but be within the BLR shell.Observations of $\it GLAST$, MAGIC, HESS, and VERITAS in the near future couldgive more constraints on the position of the gamma-ray emitting region relativeto the BLR.

Absorption of 10 Gev--1 Tev Gamma Rays by Radiation from Broad-Line Region in 3C 279