The basic features of the focal plane detector system for light particles with Beijing Q3D magnetic spectrometer have been tested by the products from 197An
12C
56Fe
C3H6N6(p
p) and (α
α ) reactions at HI-13 Tandem. Measured intrinsic position resolution is 1.36±0.07mm and the integral nonlinearity for position is 7.5 ×10-3. The identification of light particles by the ΔE-E telescope is satisfactory.