The traditional ray-casting algorithm demonstrates a range of drawbacks, such as large consumption of computing resources and a low draw speed, when drawing vast smoke data in a three-dimensional (3D) scene. Thus, a visualization method of indoor smoke based on the improved ray-casting algorithm is proposed. First, the 3D data field is divided into uniform blocks of data according to the uniform size, neutral positions of the incident and emission points are calculated when the ray travels through the blocks, and the sampling frequency is adjusted with the help of the distance ratio between the point of sight and midpoint to spot the resampling point. For sampling points at different levels, different interpolation strategies are followed by classifying the resampling points in the rays. Finally, a picture-synthesis algorithm is adopted to complete the mapping of the sampling sight data in each ray, realizing the rendering effect of indoor smoke. Experimental results show that the method is workable and effective. Compared with the existing ray-casting algorithm, the improved one considerably reduces the computing effort of resampling and linear interpolation in the rendering process on the premise of guaranteeing the authenticity and stability of the images. Moreover, the frame rate can stably maintain 75 frame·s ^-1, which can satisfy the real-time rendering requirements of smoke in different indoor scenes.