The high resolution spectra covering the wavelength range 4900 Å to 8250 Å of the hot post-AGB stars IRAS13266-5551 ( CPD-55 5588 ) and IRAS17311-4924 ( Hen3-1428 ) reveal absorption lines of C II , N II , O II , Al III , Si III and Fe III and a rich emission line spectrum consisting of H I , He I , C II , N I , O I , Mg II , Al II , Si II , V I , Mn I , Fe III , [ Fe II ] and [ Cr II ] .
The presence of [ N II ] and [ O I ] lines and absence of [ O III ] indicate low excitation nebulae around these stars .
The components of Na I absorption lines indicate the presence of neutral circumstellar envelopes in addition to the low excitation nebulae around these two hot post-AGB stars .
The H _ { \alpha } lines show P-Cygni profiles indicating ongoing post-AGB mass loss .
From the absorption lines , we derived heliocentric radial velocities of 65.31 \pm 0.34 km s ^ { -1 } and 27.55 \pm 0.74 km s ^ { -1 } for IRAS13266-5551 and IRAS17311-4924 respectively .
High galactic latitude and large radial velocity of IRAS13266-5551 indicate that it belongs to the old disk population .
Preliminary estimates for the CNO abundances in IRAS13266-5551 are obtained .