In this paper, the performances of 803 resin and its composites were studied. Dynamic DSC indicated 803 resin has high reactivity;rheological analysis proved 803 resin has excellent processing property; research of thermal behavior expressed that MT300/803 has high heatdurability, the glass transition temperture tested by DMA was 300益,Td 5 was 396益; mechanical properties showed that MT300/803 is excellent and 803 resin matches MT300 well. Therefore the MT300/803 composite has good heatdurability and can meet the needs of highproperties in the aerospace field.