The segregation of dopant inevitably affects the thermodynamic stability and electronic properties of transition metal (TM) doped TiO2 which were studied using first principles calculations. Here we show that the thermodynamic stability of doped systems is related with the doped position which is different for the considered TM dopants. The second phase could appear in V-doped TiO2 due to the VOV bonding. The thermodynamic stability and electronic properties of the doped systems will be slightly infected by dopant concentration. Moreover, the band gaps are approximately proportional to the Mulliken population values of TMO bond.