In this paper , we study the cosmic constraint to w CDM model via 118 strong gravitational lensing systems which are complied from SLACS , BELLS , LSD and SL2S surveys , where the ratio between two angular diameter distances D ^ { obs } = D _ { A } ( z _ { l } ,z _ { s } ) / D _ { A } ( 0 ,z _ { s } ) is taken as a cosmic observable .
To obtain this ratio , we adopt two strong lensing models : one is the singular isothermal sphere model ( SIS ) , the other one is the power-law density profile ( PLP ) model .
Via the Markov Chain Mote Carlo method , the posterior distribution of the cosmological model parameters space is obtained .
The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index \gamma .
Furthermore , the PLP model gives a relative tighter constraint to the cosmological parameters than that of the SIS model .
The predicted value of \Omega _ { m } = 0.31 ^ { +0.44 } _ { -0.24 } by SIS model is compatible with that obtained by Planck 2015 : \Omega _ { m } = 0.313 \pm 0.013 .
However , the value of \Omega _ { m } = 0.15 ^ { +0.13 } _ { -0.11 } based on the PLP model is smaller and has 1.25 \sigma tension with that obtained by Planck 2015 result .
This discrepancy maybe come from the systematic errors .