This paper propose a system of transmitter (TX) supported multi-protocols and variable data-width, with max input data width of 40bits and data rate of 10.3125 Gbps. The transmitter consists of Normalization of Data Width (NMDW), 40: 1MUXs, distributed clock circuit and 3-taps Feed-forward-equalizer (FFE). This paper is proposed an improved 40:1 MUXs circuit and supported in SMIC 40nm CMOS technology, supported by 1.1 V.The power consumption of TX is 34.5mW @ 10.3125 Gbps. The differential eye diagram is larger than 800 mV before channel. Meanwhile, TX is supported 4 different protocols, 7 different data-rate, 9 work conditions, the work temperature ranged from-45℃ to 125℃.