The second Fermi LAT GRB catalog presents the results for 186 Gamma Ray Bursts (GRBs) detected by the Fermi Large Area Telescope (LAT) between 2008 and 2018. Out of these, we select the GRBs with significant detection in the LAT and GBM during the T90 time interval. We further subdivide this population into four quartiles based on the fluence from the GBM and carry out joint GBM-LAT spectral analysis for the T90 duration with single and multi-component spectral models. Here, we present the results for best fit model, spectral indices, Epeak and fluence obtained from the joint analysis. We also compare the spectral properties of the four quartiles.