A 800G integrated silicon-photonic transmitter is presented, including a 16-channel photonic integrated chip (PIC) and two electrical chiplets (EICs) that are realized based on an arrayed travelling wave dual-drive Mach-Zehnder modulator (MZM) and two 8-channel CMOS drivers. The proposed multi-channel PIC is fabricated on a high-resistance silicon-on-insulator (SOI) wafer with a 220 nm thick silicon layer and a 2 μm thick buried oxide (BOX) using the foundry-ready CMOS process, while the drivers are implemented in a standard 65nm CMOS process. The driver employs a combination of distributed architecture, 2-tap feedforward equalization (FFE) and push-pull output stage, experimentally exhibiting an averaged bandwidth higher than 28.5GHz and a differential swing of 4.0Vpp on 50Ω load, respectively. The 50Gb/s electrical eye-diagram is measured with 1.41ps rms-jitter, while the optical extinction ratio (ER) exceeds 3.0dB with 5.35pJ/bit power efficiency.