  Inspired by the recent proposal for the quantum effective dynamics of the
Schwarzschild spacetime given in \cite{AOS1}, we investigate the effective
dynamics of the loop quantized Janis-Newman-Winicour (JNW) spacetime which is
an extension of the Schwarzschild spacetime with an extra minimally coupled
massless scalar field. Two parameters are introduced in order to regularize the
Hamiltonian constraint in the quantum effective dynamics. These two parameters
are assumed to be Dirac observables when the effective dynamics is solved. By
carefully choosing appropriate conditions for these two parameters, we
completely determine them, and the resulted new effective description of the
JNW spacetime leads to a well behaved quantum dynamics which on one hand
resolves the classical singularities, and on the other hand, agrees with the
classical dynamics in the low curvature region.
