<正> In order to detect light ions for RIBLL, we developed a two-dimensional positional sensitive multi-plate parallel-plate avalanche counter (MPPAC) with 100 mm×100 mm active area (as shown in Fig.1). MPPAC consists of one central anode plate, two position grid plates and two cathode plates. The position signal is read out by the charge division method with resistor chains. A position resolution of 0.55 mm (FWHM) was