Yuiyui, are you using non-buffered rendering? The latest dev builds fix the long-standing issues with buffered rendering, so you should use that unless you have the speed for Framebuffers to Memory.
If that doesn't fix it, please tell us what graphics card you have.
Edit: Don't use a build after 0.9.1-r57.
If that doesn't fix it, please tell us what graphics card you have.
Edit: Don't use a build after 0.9.1-r57.
I only use PPSSPP on Windows.
Intel Core i3 1.9GHz | 4GB RAM | Integrated Intel HD 4400 | Windows 8.1 x64
Intel Core i3 1.9GHz | 4GB RAM | Integrated Intel HD 4400 | Windows 8.1 x64