Correlation of phase formation, critical transition temperature T c , microstructure, and critical current density J c with sintering temperature has been studied for acetone doped MgB 2 /Fe tapes. Sintering was performed at 600–850°C for 1h in a flowing Ar atmosphere. High boron substitution by carbon was obtained with increasing the sintering temperature; however, the acetone doped samples synthesized at 800°C contain large size MgB 2 grains and more MgO impurities. Incomplete reaction for the acetone doped samples heated at 600°C result in bad intergrain connectivity. At 4.2K, the best J c value was achieved in the acetone doped sample sintered at 700°C, which reached 24,000A/cm 2 at 10T and 10,000A/cm 2 at 12T, respectively. Our results indicate that the small grain size and less impurity were also important for the improvement of J c –B properties besides the substitutions of B by C.