In this paper,a new designed IR Focal Plane Array Readout Integrated Circuit (FPA ROIC) is presented that can be applied to multispectral optical spectrometer.This ROIC can select the integral voltage of arbitrary contiguous or noncontiguous rows,rather than regular rows,to be readout.The function substantially improves system flexibility and frame frequency.In addition,this ROIC adopts rolling Integrate-While-Readout (IWR) mode,for which two kind of reset-integration control module is designed,according to having integration analog switch or not in unit circuit per pixel.Finally,the input stage per pixel can employ direct injection (DI),Capacitive Transimpedance Amplifier (CTIA) and so on.This ROIC has positive engineering application value.