The apicomplexan parasite Toxoplasma gondii can infect humans and almost all warm-blooded animals worldwide, poses significant threat to the public health and of veterinary importance. The acute infection was characterized by fast replication of tachyzoites inside the host cells. During this fast amplification process, the gene expression is highly regulated by series of regulator networks. The G1 phase is usually conserved across species and responsible for the preparation of materials for the next replication cell cycle, but seldom regulators were identified in this stage. Here, we functionally characterized the C/G1 phase expressed ApiAP2 transcription factor TgAP2XII-8 in T. gondii tachyzoite. Conditionally knockdown of TgAP2XII-8 leads to significant growth defects and asexual division disorder. Additionally, the parasite cell cycle progression was also disrupted after TgAP2XII-8 depletion, which is characterized by G1 phase arrest. RNA-seq and CUT&Tag experiments revealed that TgAP2XII-8 played as an activator for the ribosomal proteins expressed in G1 phase. Moreover, TgAP2XII-8 bind to a specific DNA motif ([T/C]GCATGCA), which is abundant and conserved in the intergenic region of several other apicomplexans, which may suggest a broad and conserved role for this ApiAP2 in the Phylum of Apicomplexa. These data provide important knowledge for the understanding of transcriptional regulation of parasite cell cycle in T. gondii. Overall design: To assess the functions of TgAP2XII-8 in T. gondii, an indole-3-acetic acid (IAA) degradation (mAID) system was used to generate an inducible knockdown (iKD) of TgAP2XII-9 parasites (iKD TgAP2XII-9). Potentially regulated genes of the transcription factor TgAP2XII-8 were investigated by RNA-seq using TgAP2XII-8 iKD parasites with or without IAA treatment for 12 or 24 hours. Three biological replicates were employed. To further characterize the direct target genes of TgAP2XII-8, CUT&Tag experiments were performed using the endogenously 3xHA tagged parasite and RH strain.