This paper proposes a simple optimal reactive power flow (ORPF) model in mixed polar form based on the dummy nodes transformer model. By introducing voltage magnitude variables at the dummy nodes to express the transformation relationships of the power and the voltages of ideal transformers, the proposed model does not need to consider the variables of transformer ratios directly. So the power equations of the transformer branches do not contain complex items multiplied by the squares of variables, but drop from four-dimensional variables of the transformer equivalent circuits to three-dimensional variables. It simplifies the ORPF model efficiently and solves the problem of the traditional model which is a little complicated and hard to calculate. The calculation results of IEEE-30, -57, -118, and -300 bus systems show that the proposed model converges quickly and the number of iterations reduce by more than half compared to the traditional model. With higher computational efficiency and more stable numerical property, the proposed model is suitable for practical application in large-scale power systems.Hua Wei (Non-member) received the M.S. degree from Guangxi University (GU), Nanning, China, and the PhD. degree from Hiroshima University, both in power engineering. Now he is a Professor of electrical engineering, GU. His research interests include power system operation and planning, in particular the application of optimization methods to power systems. Prof. Wei is a member of the CSEE and IEEE.Chunmei Lin (Non-member) received the B.E. degree in electrical engineering and automation from Guangxi University (GU), Nanning, China, in 2014. Currently, she is a postgraduate student at the Guangxi Key Laboratory of Power System Optimization and Energy Technology, GU. Her current research interests include power system optimization.Yufei Wang (Non-member) received the B.E. degree in technique and instrumentation of measurements