The observability analysis is a key problem of SOPLAT (single observer passive location and tracking).Becauseofthehigh nonlinear of TOA measurement equation, the observability matrix which is got by calculating Jacobin matrix is toocomplextoobtain explicit analysis conclusions. A linearization equation is deduced through a new idea, and the observabilityconditionsofSOPLAT using TOA and DOA measurements are obtained. Finally, a compute simulation result is presented.