Accurate localization of weak seismic sources remains challenging in complex media, and conventional reverse time imaging is often sensitive to noise and wavefield interference. To address these issues, we propose a two-dimensional time-domain contrast-source reverse time imaging method based on scattering theory. Using a smoothed background model as a reference, the medium perturbations were reformulated as equivalent contrast-source terms. This formulation established an explicit physical link between the scattered wavefield and medium heterogeneity, enabling efficient simulation of scattering responses. Conventional cross-correlation imaging conditions are frequently dominated by high-energy channels and amplitude imbalance among receivers. We therefore developed a grouped cross-correlation imaging condition with energy normalization. This strategy suppresses the dominance of strong-energy channels and enhances coherent stacking across different receiver azimuths, leading to improved focusing and more stable source localization. Numerical experiments were conducted on a simple scatterer model and the Marmousi velocity model. The proposed method was compared with conventional finite-difference reverse time imaging under different noise levels and multi-source scenarios. Results demonstrate that the contrast-source-based approach provided clear advantages in characterizing weak scattering signals, noise robustness, and energy focusing. The proposed grouped energy-normalized imaging condition further improved imaging resolution and source detectability. These results indicate that the proposed method is stable and adaptable in complex media, offering a promising imaging framework for microseismic and other passive-source localization. The method also shows potential for extension to three-dimensional elastic wave equations and real field data.