Coherent LiDAR systems face challenges in long-distance target detection due to weak echo signal energy and interference from external factors such as atmospheric turbulence, resulting in low signal-to-noise ratios (SNRs) and reduced detection performance. To address these issues, we propose a joint temporal and spatial enhancement technique based on a coherent radar system with multiaperture reception to optimize the extraction of weak signals. The proposed technique improves the SNR and detection performance by extending the accumulation period in the temporal dimension and increasing the number of receiving apertures in the spatial dimension. The theoretical simulations and experimental results demonstrate the effectiveness of the proposed method. Specifically, temporal and spatial accumulation methods yield SNR gains that are consistent with the theoretical predictions. For varying accumulation times of single-aperture echo signals and equivalent accumulation times of multiaperture echo signals, the expected improvements are achieved. By combining spatial and temporal accumulation, weak echo signals with power as low as 0.56 fW are detected under conditions involving 36-aperture spatial accumulation and 20-ms temporal accumulation, achieving an SNR of 24.3 dB. The proposed technique significantly enhances the capability of coherent LiDAR systems to detect weak signals and thus holds important practical application value.