GauStudio is a modular framework for 3D Gaussian Splatting (3DGS) that enables flexible and customizable scene modeling. It provides standardized, plug-and-play components for users to easily customize and implement a 3DGS pipeline. The framework supports a hybrid Gaussian representation with foreground and skyball background models, which reduces artifacts in unbounded outdoor scenes and improves novel view synthesis. Additionally, it introduces Gaussian Splatting Surface Reconstruction (GauS), a novel render-then-fuse approach for high-fidelity mesh reconstruction from 3DGS inputs without fine-tuning. GauStudio's modular design allows different components to be flexibly combined and replaced, enabling the convenient construction of different 3D scene modeling methods. The framework includes several key stages: scene initialization, Gaussian optimization, enhancement, and compression. It also considers various representations for encoding view-dependent appearance within the Gaussian splats, including spherical harmonics, learned neural feature vectors, and explicit feature caching structures. GauStudio also provides an efficient surface reconstruction module, GauS, which converts 3D Gaussians into textured triangle meshes. This module is compatible with various GS-based methods and can easily extract meshes for different types of Gaussians with a single command. For background modeling, the framework uses spherical environment maps composed of Gaussians. All modules are fully customizable in GauStudio. The framework's key contributions include a modularized and composable Gaussian Splatting framework, a framework that encapsulates many key stages in 3D Gaussians reconstruction, and an efficient mesh extraction pipeline, GauS, to convert optimized Gaussians into textured meshes. Overall, GauStudio presents a comprehensive yet customizable platform to drive innovation in 3D scene modeling tasks like reconstruction, editing, and simulation.GauStudio is a modular framework for 3D Gaussian Splatting (3DGS) that enables flexible and customizable scene modeling. It provides standardized, plug-and-play components for users to easily customize and implement a 3DGS pipeline. The framework supports a hybrid Gaussian representation with foreground and skyball background models, which reduces artifacts in unbounded outdoor scenes and improves novel view synthesis. Additionally, it introduces Gaussian Splatting Surface Reconstruction (GauS), a novel render-then-fuse approach for high-fidelity mesh reconstruction from 3DGS inputs without fine-tuning. GauStudio's modular design allows different components to be flexibly combined and replaced, enabling the convenient construction of different 3D scene modeling methods. The framework includes several key stages: scene initialization, Gaussian optimization, enhancement, and compression. It also considers various representations for encoding view-dependent appearance within the Gaussian splats, including spherical harmonics, learned neural feature vectors, and explicit feature caching structures. GauStudio also provides an efficient surface reconstruction module, GauS, which converts 3D Gaussians into textured triangle meshes. This module is compatible with various GS-based methods and can easily extract meshes for different types of Gaussians with a single command. For background modeling, the framework uses spherical environment maps composed of Gaussians. All modules are fully customizable in GauStudio. The framework's key contributions include a modularized and composable Gaussian Splatting framework, a framework that encapsulates many key stages in 3D Gaussians reconstruction, and an efficient mesh extraction pipeline, GauS, to convert optimized Gaussians into textured meshes. Overall, GauStudio presents a comprehensive yet customizable platform to drive innovation in 3D scene modeling tasks like reconstruction, editing, and simulation.