Abstract: The rheological behaves of polyether-ether ketone (PEKC)-bismaleimide (BMI) system during isothermal curing was studied by in-situ rheology. The time and temperature dependence were discussed in detail. The influence of PEKC contents on the viscosity of the PEKC-BMI blends was investigated. The results show that the gel point of BMI resin is of the frequency dependence, while tanδ is frequency independent. The viscosity increase of PEKC-BMI resin system is caused by PEKC dissolving in BMI and BMI curing with the increasing temperature. Comparison of 110℃ with 130℃ shows that, at higher temperature, the viscosity increase of the composite resin system is mainly caused by BMI resin curing. As the temperature increase, the gel time with increasing PEKC content shortens more rapidly, while the gel modulus increment becomes less. However, at lower temperature, the gel modulus increment becomes more with increasing PEKC content. With PEKC content of the resin system increasing, the apparent activation energy of gelation reaction increases from 4.9 kJ/mol to 65.9 kJ/mol. It is indicated that the temperature sensitivity of gelation behavior increases.