Films of poly vinyl alcohol (PVA) /poly vinyl pyrrolidone (PVP) blends have been prepared by solution casting method with different ratios of each other (100/0 , 80/20 , 60/40 , 50/50 , 40/60 , 20/80 , 0/100) to investigate their thermal stability comparing to correspondent pure polymers by using thermogravimetric analysis (TGA) under air atmosphere. It was found that PVA and PVP films show two decomposition steps while PVA/PVP blend films show three decomposition steps except the film of the ratio (20/80) that shows four decomposition steps .It was also found that blending decreases the temperature ranges at which the first and the second decomposition steps of PVA and PVP occur. It was found that blending PVA with PVP has significant effect on weight loss at first decomposition step of PVA by increasing it as the ratio of PVP increases. It was also found that blending PVA with PVP has significant effect on weight loss at second decomposition step of PVA by decreasing it as the ratio of PVP increases. It was found that the weight loss at third decomposition step of PVA/PVP blend films increases as the ratio of PVP increases . According to TGA thermograms under air atmosphere, PVA , PVP and PVA/PVP blend films show almost the same total weight loss which means of same thermal stability.