We propose a theoretical model to detect the quantum phase transition in a triangular quantum dot molecule with frustration.The boundaries of the phase diagram are accurately determined by the transmission.For small frustration t,as the interdot Coulomb repulsion V increases,the system undergoes a Kosterlitz-Thouless (KT) transition from the Kondo resonance state with a transmission peak at zero energy to the Coulomb blocked state with zero transmission,which is followed by a first transition to the V-induced resonance (VIR) state with unitary transmission.For large frustration t,as V increases,the orbital spin singlet without transmission transits to the VIR state through a KT transition.