Approximately half of the world’s languages are tonal, and how lexical tone is encoded in spoken word production is still unclear. In Mandarin word production, there are two contrasting views regarding the mechanisms of tonal encoding. The two-stage model assumes that the lexical tone is selected first at the early stage of production, and then integrated with the atonal syllable at the later stage, while other researchers proposed that the lexical tone is retrieved only at the later stage of production. In this study, we performed computational simulations on disyllabic words to uncover the mechanisms underlying the facilitation and interference effects on naming latencies observed in previous primed picture naming studies, which intended to verify the two theoretical accounts of tonal encoding in Mandarin spoken word production. The results supported the two-stage model of tonal encoding in disyllabic Mandarin word production. Increased inhibition between atonal syllables and decreased activation between the tonal frame and the syllable motor program, implying slower tone-to-syllable integration, appear to be the prerequisite for generating the interference effect of tonal overlap without shared syllabic information.