Under the harsh environment in which the number of visual navigation satellites is less than four and traditional navigation solution cannot be completed, the navigation receiver can enter the emergency auxiliary positioning mode by equipping the user with external elevation barometer providing for elevation information, or with internal punctuality module providing for clock bias. The traditional navigation and positioning error propagation model cannot be applied to analyze the error in this emergency assisted positioning mode. To solve this problem, this research focused on the basis of several emergency auxiliary positioning principles, such as three satellites combined with the elevation, three satellites combined with clock bias, two satellites combined with elevation and clock bias, and provided a new error propagation analysis model of emergency auxiliary positioning, verifying the correctness of the model by simulation example. Finally, through the positioning accuracy analysis, it concluded that the present method can quantify the optimal magnitude relations between pseudorange measurements and the accuracy of the auxiliary information with minimum cost to improve positioning accuracy, which can guide the choice of external auxiliary devices for navigation receiver.