Abstract: To investigate the crack control mechanism and performance improvement paths of steel fiber geopolymer lightweight aggregate concrete (SFGLAC), eight SFGLAC bending specimens were subjected to four-point bending tests. The effects of coarse aggregate volume fraction, reinforcement ratio, span length, and concrete strength on the failure mode, bending capacity, and crack distribution of the beams were analyzed. Fractal theory was applied to analyze the crack morphology and propagation behavior of SFGLAC beams, and a crack width analysis model for these beams was developed based on the thick-walled cylinder theory. The test results indicated that all specimens exhibited typical bending failure, with failure modes and crack propagation behaviors similar to those of ordinary plain concrete beams. The cracking load of the specimens was approximately 10% of the ultimate load (Mu). The cracks were numerous and closely spaced, and the fractal characteristics of the cracks were clearly evident under different loading conditions. The fractal dimension of the cracks accurately characterized the crack morphology and distribution, showing a significant correlation with the bending performance indicators of the specimens (R² > 0.97). The average ratio of predicted to experimental crack width values was 1.111 ± 0.015, demonstrating high accuracy and applicability of the model. The findings provide a theoretical basis for the design optimization, performance enhancement, and structural health monitoring of steel fiber geopolymer lightweight aggregate concrete.