In this article, a phosphorus containing bismaleimide (V) based on 2-(6-oxido-6H-dibenz [c,e] [1,2]6-yl)-1,4-dihydroxy phenylene (I) was synthesized and copolymerized with 4,4＇-bismaleimidodiphenylmethane (BMDM) in various weight ratio (0-33 phr). DSC scans show that the introduction of V into BMDM has increased the processing window for the resulted copoly(bismaleimide). DMA scans show these cured BMIs exhibit good modulus ( similar to 2 GPa) up to 400 degrees C. There is no tangent peak for these cured BMIs implying that there is no relaxation below 400 degrees C. TMA scans show introduction of V into BMDM increase the coefficient of thermal expansion (CTE). However, CTE of these cured BMIs are less than 50 ppm, which is much less than common epoxy. There is no second transition during TMA heating scans up to 440 degrees C, so T(g)s of these cured BMIs are higher than 440 degrees C, which is consistent with the DMA measurement. TGA heating scans also indicate that they have high thermal stability and their char yields increase with the content of V. Char yields at 800 degrees C shift from 48 to 63 in nitrogen and from 0 to Is in air when 25 phr of V was introduced into BMDM. TGA isothermal experiments show that these cured BMIs are thermally more stable in air than in nitrogen below 450 degrees C. Char yields also increase with the content of V.