Based on the production and transportation of the fluorescence in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal,a simulation model has been setup using the GEANT4 codes for a small gamma camera with WSFs coupled to a YAP scintillation crystal. An advantage of this technique over direct readout with a position-sensitive photo-sensor is small amount of readout channel could be used for the same image area. Simulation results show that at least 15 photons on average for 59.5 keV gamma ray (²⁴¹Am). A spatial resolution of 1.28 mm FWHM is obtained when silicone grease is used to couple to the fibers to the crystal. The factors affecting the number of photons and the spatial resolution are discussed.