Pulse-by-pulse single-shot spectrum measurement can be realized using the time stretch dispersive Fourier Transform technique. In this paper, we report a fully integrated and modular pulse-by-pulse single-shot optical spectrum analyzer (PS-OSA) system. Many modules including a picosecond gain-switched laser, multiple fibers with different chromatic dispersions, high-power optical amplifiers, a clock-generator, a photodetector and a digitizer are integrated into a main-frame. These modules are standard in size and can be replaced to improve the performance or changed to adapt the system to different applications. Here, we present the specification of this single-platform PS-OSA and successfully demonstrate high throughput measurement of the transmission spectrum of electroabsorption optical modulators with 11.7 ns refresh time.