3D Gaussian Splatting (3DGS) has demonstrated impressive performance in novel view synthesis and real-time rendering. However, it heavily relies on high-quality initial sparse points from Structure-from-Motion (SfM) which often struggles in textureless regions, degrading the geometry and visual quality of 3DGS. To address this limitation, we propose a novel initialization pipeline, achieving high-fidelity reconstruction from dense image sequences without relying on SfM-derived point clouds. Specifically, we first propose an effective depth alignment method to align the estimated monocular depth with depth rendered from an under-optimized coarse Gaussian model using an unbiased depth rasterization approach and ensemble them afterward. After that, to efficiently process dense image sequences, we incorporate a progressive segmented initialization process that to generate the initial points. Extensive experiments demonstrate the superiority of our method over previous approaches. Notably, our method outperforms the SfM-based method by a 14.4% improvement in LPIPS on the Mip-NeRF360 datasets and a 30.7% improvement on the Tanks and Temples datasets.