In Indonesia, the famous method of the salt production process is evaporation using solar energy. The important aspect of this method is the evaporation rate. The evaporation rate is nearly related to the physical conditions of the surrounding environment. The aim of this study is to determine the evaporation rate of raw water in the production process using a prototype and determine the effect of physical parameters on the rate of evaporation of raw water in the production process in the salt house. The causal method with a quantity approach was used in this research. The results obtained are the total evaporation rate on the prototype at the Salt House is 1.68 litters/day and the results of Spearman rank correlation show that luminous intensity, air temperature, and wind speed have a significant impact on the evaporation rate because the significant value is <0.005 while the humidity level is not s significant effect.