In this paper the effect of the ionospheric delay on passive radar using opportunity transmitters is addressed. We establish analysis models and methods on the effects of the ionosphere on passive radar using opportunity transmitters. Ionospheric data TEC（total electron contain）for 15 days published by IGS(international GPS service) are used to study the influence of ionospheric delay. Both low Earthorbiting spacecraft and geostationary are considered. Simulation results show that the positioning error caused by ionospheric delay presents the eastward migration, the positioning error of geostationary can up to several meters, and the positioning error of low Earthorbiting spacecraft can up to several meters.