Abstract: For navigation satellite’s orbit eccentricity is equal to zero approximately, it would result in the ambiguity of satellite orbit’s argument of perigee and the singularity of the normal matrix in the process of fitting. The new broadcast ephemeris parameters fitting algorithm is developed and it deduces the partial derivative matrix of satellite position vector with respect to modified parameter based on the non-singular transformation. At last, the rationality of formulas and algorithm are validated by simulation.

Key words: Broadcast ephemeris parameters, Non-singular transformation, Least square fitst tracking