An optimized comprehensively analytical thermal model was developed in accordance with interior heating characteristics of a gain-guided, top-emitting vertical-cavity surface-emitting laser with c.w. operation under room temperatures. Lateral thermal effects in AlInGaAs/AlGaAs vertical-cavity surface-emitting lasers were calculated analytically in detail. The comprehensively analytical solutions exhibited a clearer physical picture of the lateral heat-flux diffusion. The theoretical predicts of the interior thermal variation within the device were consistent with the experimental results as well. The work provides a useful tool for investigation of thermodynamic properties of the vertical-cavity surface-emitting lasers under thermal steady state, optimization of the device structure and control of the threshold current and power saturation effect, especially for the lateral thermal crosstalk in 2-dimensional arrays.