Beidou satellite broadcast ephemeris is the main error source of timing service, and it is necessary to analyze its precision. The calculation method of signalinspace is analyzed mainly considering satellite ephemeris and satellite clock error. The care must be taken is that when using the BeiDou satellite broadcast ephemeris and precise ephemeris/clocks the reference time scale is atypsim, the coordinate system is atypsim, and the reference point of satellite position is atypsim. The impact of signalinspace error on oneway timing is analyzed with IGS final precise ephemeris for reference. According to the results, the random fluctuation of the impact of signalinspace error on oneway timing is within 7 ns. And the impact of satellite clock error is relatively larger than that of satellite ephemeris error because there are different system errors corresponding to each BeiDou satellite’s clock error.