Based on the mathematical model for the tooth form analysis of spiral bevel gears, the tooth form errors between the theoretical tooth flank and the inaccurate one, in the normal direction of the theoretical tooth flank, were calculated by applying optimization algorithm and a new computing method. By introducing the machine setting errors and cutter parameters errors, the effect of various errors on the tooth form of spiral bevel gears was analyzed. The deviating direction from the theoretical tooth flank and the values of tooth form errors were expressed by graphics. The results provide a reference for precision design of machine tools, correction of tooth form errors and practical processing. The algorithm and analysis results are validated via experiment.