Distributed generations are renewable sources that do not create environmental pollution and install near the site of consumption. Also, the generated power of wind and solar sources are faced with uncertainty due to the dependence on external factors. With determination of the appropriate location and size of these sources in distribution networks their positive effects can be realized. But it must be noted that distribution networks due to the unequal phase loads and mutual impedance between various phases of lines are virtually unbalanced. So in this paper, determination of the appropriate size and place of distributed generations is done in unbalanced distribution network that distributed generations’ appropriate size obtained with respect to probabilistic methods and their convenient location is selected using weighted multi-objective IPSO algorithm. With regard to impact of exact load flow in calculations, linear three-phase unbalanced load flow method considering the loads model and loads connection type is used which is the fast and accurate unbalanced load flow method. Simulations are done in IEEE 37 bus unbalanced network in Matlab software. The simulation results indicate that network power losses and voltage unbalance factor are reduced, voltage profile of each phase is improved and significant profit is obtained for distribution companies