We evaluated the doping effect of single walled carbon nanotubes (SWCNT) on the phase formation, microstructure, critical current density ( ), and upper critical field ( 2) of MgB2 superconductor. All samples were sintered at temperatures ranging from 650 to 1000 C for 30 min. A typical high sintering temperature (900 C) sample was composed of well-consolidated MgB2 grain of 100 to 200 nm and nanosized particles, resulting in enhancement of and 2. This indicates that lattice defects and microstructural change have occurred as a result of carbon (C) coming from SWCNT. On the other hand, a sample sintered at low temperature (700 C) contained relatively large grains. Specifically, SWCNT dopedMgB2 wire sintered at 900 C exhibited excellent 104 Acm 2 up to 8 T at 4.2 K. This result indicates that flux pinning for sample produced at a high sintering temperature are enhanced by SWCNT doping. SWCNT is one of the promising C sources for MgB2 superconductor with excellent .