Although the performance of TCP-Vegas protocol is superior to the traditional TCP protocol, its performance will get worse in high-speed MANET due to the high-speeded node and frequently changed topology. So a new kind of optimized algorithm is promoted to apply to the high-speed MANET avoiding its potential worseness on the basis of TCP-Vegas protocol. On the phrase of congestion avoidance, optimized algorithm will adjust the size of congestion window, at the same time, it will observe both the difference of the expected throughput and the actual throughput, and the changes of tote hop. According to the results of simulation, new optimized algorithm in high-speed MANET performs better than that of tht TCP-Vegas protocol.