To achieve textured surfaces with superior friction reduction properties, it is crucial to investigate the impact of laser surface texturing technology on wettability. Based on the wettability theory, the rectangular area method was proposed to analyze the relationship between different micro-pit textures and wettability. With this method, the variation of hydrophilic textured surface wettability was explored through the morphology, spacing, and size of micro-pits. The fiber laser was used to process diamond-shaped, round, and square micro-pit textures with different spacing of 0.1, 0.2, and 0.4 mm and dimensions of 0.1, 0.2, and 0.4 mm on the surface of the 316L stainless steel. The contact angles of the smooth stainless steel and the surface of the micro-pit texture were tested by a contact angle measuring instrument. The surface roughness factor was calculated by the Wenzel model. Through the theory of the rectangular area method, mathematical models were established for the surface roughness factors of different micro-pit textures. The the roughness factor was obtained with the rectangular area method by calculating the ratio of the actual contact area of the solid-liquid interface in the rectangle to the rectangular area. The wettability of the textured surface of the groove was analyzed by the rectangular area method. It was found that increasing the groove spacing resulted in a decrease in the roughness factor, an increase in the contact angle, and a weakening of the wettability. In addition, when the size of the micro-pit texture remained the same, the wettability decreased with the increase in spacing. When the roughness coefficient was the same, the larger the texture area in the rectangle, the stronger the wettability. When the size and spacing were equal, the wettability was the strongest. In the range of this experiment, the wettability of the square micro-pit texture with a dimension of 0.1 mm and a spacing of 0.4 mm was the strongest, and the contact angle was 30.6°. The trend analysis of textured surface changes obtained through contact angle testing aligned with the conclusions drawn from the proposed rectangular area method, confirming the feasibility of the rectangular area method. In order to verify the accuracy of the model, the test results of the contact angle were quantitatively analyzed with the predicted values of the model. The results showed that the roughness factor calculated by the rectangular area method was slightly lower than the roughness factor calculated by the actual contact angle. This might be due to the V-shaped cross-section of the micro-texture prepared by the fiber laser, and due to the presence of the recast layer, the interior of the micro-pit was not a smooth plane, which made the true area of the micro-pit texture greater than the theoretical area of the micro-pit texture. In addition, the tiny bumps inside the micro-pits were irregular and difficult to calculate. In order to more accurately calculate the roughness factor of different micro-pit textures, a correction factor K was introduced in the theory of the rectangular area method, and the relevant regression equation (R2=0.997 5) was established, thereby improving the roughness factor prediction model. The larger correlation index showed that the regression equation was accurate and effective. The method provides a reference basis and an optimization method for processing textured surfaces with excellent wettability.