Abstract: The slope angle (or top angle) of the building significantly influences the formation of upward leader. To simulate the lightning strike process on tall and sloping building using three-dimensional variable grid leader model, the influence of slope angle (θ) on the initiation of stable upward leaders is analyzed, focusing on various building heights (H_b) and peak values of lightning current (I_p). It can be concluded from data that, when the peak lightning current is held constant, reducing the building height and increasing the building width result in an enhanced influence of the slope angle on stable upward leader inception (η), which in turn makes it increasingly challenging to incept. When the height of building is held constant, a reduction in the peak value of lightning current enhances the influence of slope angle on the inception of stable upward leaders (η). This, in turn, makes the inception process increasingly challenging. Changes in building width have a lesser impact on the initiation of the upward leader compared to building height. As heights of buildings and peak values of lightning currents increase, the influence of slope angle on the initiation of stable upward leader becomes less significant. By conducting a multiple linear regression analysis with η as the dependent variable and slope angle (θ), building height (H_b), and peak lightning current (I_p) as independent variables. Results indicate that I_p and H_b have a significant negative effect on η, whereas θ has a positive effect on η. The degree of influence on η is as follows: I_p has the greatest influence, followed by θ, while Hb has the least influence. The influence of slope angle on the inception of stable upward leaders, represented by the parameter η, is significant for building heights below 100 m and peak lightning current values below 40 kA, with the estimated effect exceeding 23.32%. In contrast, for building heights exceeding 500 m and peak values of lightning current above 100 kA, the impact of slope angle on stable upward leader inception is relatively minimal, with an estimated effect of less than 15.88%, in the case, the distinction between the impact of sloped buildings and rectangular buildings on the inception of stable upward leader is sufficiently marginal to enable an approximate analytical approach.