The multi-blade wind turbine is a type of wind turbine that has been used by salt farmers in Paccelang Village, Jeneponto Regency, South Sulawesi Province. In operation, turbines often experience damage due to excessive vertical deflection of the shaft. This article examines and identifies the parameters that cause the vertical deflection of the shaft. The research was carried out theoretically and numerically. Theoretically, the research was carried out by entering the corresponding parameters into the described shaft vertical deflection equation. Numerically, the research was conducted using software inventor. In part I of this article only shows the results of theoretical studies. The parameters that cause excessive vertical deflection of the shaft and sorted by the magnitude of the contribution are reduction in shaft diameter, shaft elongation, and enlargement of external load
