Dust on the surface of the photovoltaic panels is one of the main factors affecting solar photoelectric (PV). In this paper, various factors were considered to analyze the effect of dust on the PV panels in Tianjin, China. A typical orientation multi-dip test platform was built to test the transmission of solar PV panels in the outdoor for 6 months. The results showed that the southward PV panels were affected by wind velocity and direction more than others. Dust on southward PV panels increased rapidly at first, then decreased under the influence of rainfall, the dust on southward PV panels placed at 45°for 70 days were 28.05%, 14.91% and 3.68% higher than that in the eastward, westward and northward, respectively. Without rainfall, the dust on southward PV panels placed in 45° for 30 days was 1.90% lower than that in the eastward, and 7.32% and 11.95% higher than those in the westward and northward, respectively. The functional relationship between dust density and dip angle was established by regression analysis. This study can provide measured data and basic theoretical support for the design and operation and maintenance of PV and photo-thermal systems.