The results of photometric CCD monitoring and spectral observations of the black hole binary and microquasar V4641 Sgr in the quiet state are presented .
The ellipsoidal light curve with large amplitude of 0 ^ { m } .36 in R band suggests the influence of a massive object orbiting around a normal B9 star .
In the spectra taken with the 6-m telescope one hour before black hole inferior conjunction , an absorption component in the red wing of H \alpha line is visible .
It is formed by gaseous stream moving in the direction to the normal star .
That suggests the grazing conjunction in this system .
Maximum velocity of the stream is of 650 km/s .
Assuming that the stream is moving through the circular Keplerian orbit around black hole , the mass of the black hole is determined to be M _ { BH } =7.1 - 9.5 M _ { \odot } , what confirms the model by Orosz et al .