O 7-δ samples (0.0 ≤ x ≤ 0.6) is prepared by the standard solid state reaction technique. X-ray measurements confirm the formation of the 123 phase for x ≤ 0.3, but for 0.4 ≤ x ≤ 0.6, due to the solubility limit, the 123 phase is not a dominant phase. Resistivity measurements show the increasing of resistivity with the increase of Ba-doping up to about x=0.08, and then decreases in the 123 phase up to x = 0.3. There is no observation of superconducting state in our samples, but we observe the sharp decrease of resistivity for x>0.1, which is related to possible superconductivity in Pr123 system by Ba-doping. It is concluded that the Pr/Ba disorder has important effect in the transport electrical properties, specially occuring a superconducting state in Pr123. It is also suggested that extra Ba concentration in Pr123 system can create superconducting state such as in Ca-doped Pr123.1 Introduction Although, tremendous amount of research have been carried out for understanding the high temperature superconductivity (HTSC) mechanism, there is not yet any complete theory for describing it. Research on metal-insulator and superconductor-insulator transitions (MIT & SIT), magnetic transitions, and phase diagrams can help us to this understanding. One singularity in the rare earth-based HTSC is the suppression of superconductivity in RBa 2 Cu 3 O 7 (R123) family (R is Y and rare earth elements except Ce, Pm, and Tb) by Pr-doping in the Ba [1] or R [2] sites, and then, the Pr123 system is the only R123 orthorhombic structure with insulator behaviour. So, the role of Pr in the superconductorinsulator anomaly could help to understand the mechanism of superconductivity, at least in R123. Models such as pair breaking [3], hole filling [4], hole localization [5], and Pr/Ba disorder [6] have been considered for explaining this anomaly. Within these models, no single complete and convincing model exists for describing the experimental data on the Pr anomaly. Ref. [7] gives a more complete survey on these models for solving the Pr anomaly.While, many researchers are seeking to find the answer to the insulating Pr123 through new models or the combination of the above models [8], some groups have reported superconductivity in thin films [9], single crystal [10], and powder and film samples [11] of Pr123. These observations have caused some confusion on the Pr anomaly, and renew the study of the Pr anomaly by the Pr/Ba disorder in RPr123. In some recent reports, the nominal substitution of Pr at Ba site has been discussed for the determination of the role of Pr/Ba disorder in the anomalous behaviour of Pr123. So, before attempting to solve the Pr problem, it should be settled whether Pr123 is really a superconductor or an insulator. Zou et al. is one of the groups who have reported superconductivity in Pr123 in their samples grown by travelling-solventfloating-zone (TSFZ) method [12]. Of course, this observation is in contrast to many other reports indicating that Pr123 is indeed on insulator. Observation of superconductivity in Pr ...