We study the properties of a quantum critical region of an XXZ model in 2D. The quantum critical point at zero temperature evolves as the temperature increases. Using the quantum Monte Carlo method with stochastic series expansions, we obtained the phase diagram. For the finite-temperature transitions from a paramagnet to an XY critical phase, we measured the superfluid stiffness and used the finite-size scaling to obtain the critical temperatures. For the paramagnet-to-antiferromagnetic transitions, we measured the compressibility to obtain the critical points.