Based on the 70 nm InP HEMT process， a 230~250 GHz low noise amplifier terahertz integrated circuit （TMIC） is designed. The amplifier adopts cascade structure of five common-source amplifiers to achieve low noise amplification. Based on the bias network which consists of microstrip radial stub and transmission line to isolate RF signals and DC bias signals. The first and second stages of the amplifier are designed based on noise matching technology， the middle two stages are designed based on power matching technology， and the last stage focuses on output matching. The on-chip test results show that the small signal gain of the LNA is greater than 20 dB in the frequency range of 230~250 GHz. The Y-factor method is used to complete the noise test of the encapsulated low noise amplifier module. The noise figure of the MMIC amplifier is better than 7.5 dB in the frequency range of 243~248 GHz. Compared with HBT and CMOS processes， the low noise amplifier based on HEMT process has a noise figure advantage of more than 3 dB.