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[Objectives] In this paper, struvite crystallization approach was used to treat anaerobically digested food-waste slurry in order to recover ammonia nitrogen. [Methods] We investigated the effects of temperature, the reaction time, initial pH value, and the molar ratio of magnesium to phosphorus to nitrogen on the recovery of ammonia nitrogen by struvite crystallization approach. Furthermore, struvite crystallization effectiveness of keeping a constant pH value throughout the trial and only adjusting initial pH value were also compared in the study. [Results] The results showed that adjusting initial pH value instead of keeping constant pH value was beneficial to removing or recoving ammonia nitrogen due to the struvite formation of a higher purity. Optimum parameters including reaction temperature of 28°C, initial pH of 9.0, the reaction time of 90 min, and the mole ratio of magnesium, phosphorus and nitrogen with 1.43:1.3:1 were observed for obtaining the highest removal efficiency of ammonia nitrogen, and the main component of the precipitate was identified as struvite by detection. [Conclusions] Under the optimal conditions, the removal rate of ammonia nitrogen can reach 98%. After struvite crystallization, the residual ammonia nitrogen and phosphate in anaerobically digested food-waste slurry were drastically reduced to 48.74 and 35.35 mg·L-1, respectively. As a result, the ratio of the chemical oxygen demand(COD) to total nitrogen content(TN) in slurry was enhanced by about 8 times, which would improve subsequent wastewater purification by activated sludge process. [ABSTRACT FROM AUTHOR]