The solar radiation pressure (SRP) is one of many forces acting on orbiting satellites. It has been the most difficult force to model for satellites at medium Earth orbit altitude and hence the biggest error source in GNSS orbit determination. NGS uses 5 parameter Empirical CODE Orbit Model (ECOM) to model SRP acting on GPS satellites. However, several researchers have shown its deficiency in modeling SRP acting on other GNSS satellites, such as GLONASS, Galileo and BeiDou satellites. To address this deficiency in the traditional ECOM model, a new model, called Extended ECOM, has been proposed in [Arnold, 2015]. The Extended ECOM introduces more parameters to represent SRP acting on GNSS satellite in addition to the 5 parameters in the traditional ECOM model. We have tested the performance of several variations of the Extended ECOM model on GNSS orbit determination by making use of the approach called orbit fit analysis. In orbit fit analysis, the performance of force models is evaluated by comparing the propagated ephemeris to the high quality precise ephemeris products. We used GNSS precise ephemeris products from IGS MGEX working group. In this poster, we present the results from this effort.