Abstract: Tropospheric delay is one of the main error sources that affect the accuracy of Global Navigation Satellite System (GNSS) navigation and positioning. One effective way to weaken the influence of tropospheric delay is the model correction method. This paper has proposed a simple and accurate fusion tropospheric delay model (FZTD) by combining the simplicity of the UNB3 model and the high-precision characteristics of the GPT2w model. The accuracy of the purposed model was verified by using the International GNSS Service (IGS) troposphere zenith delay (ZTD) data over 2011—2015. The results show that root mean square (RMS) and bias values of the FZTD model are 4.4 cm and −0.3 cm, respectively, which are smaller than the traditional models UNB3m (RMS: 5.1 cm, bias: 1.1 cm) and EGNOS (RMS: 5.1 cm, bias: 0.3 cm). Its global accuracy has increased by 14%, and the improvement is particularly obvious in the southern hemisphere, especially in the Antarctic region, the accuracy has increased by nearly 3 times. The FZTD model makes up for the shortcomings of the traditional models that there are large differences in accuracy between the northern and southern hemispheres. The total meteorological parameters of the new model are only 120, which are drastically reduced compared to the GPT2w model, which makes it possible to be hardwired in the GNSS receivers.