To solve the contradiction among the sensitivity, the dynamic range and the microwave performance of the on-line microwave power sensor fundamentally, a coupled on-line MEMS microwave power sensor is designed creatively in this article. It makes the extraction and detection of microwave power independent of each other. According to the theoretical analysis model, the relationship of the sensitivity characteristics with the coupling degree is obtained, and the differences are analyzed and compared in microwave characteristics and sensitivity characteristics when the coupling degree are 10% and 20% , respectively. Experimental results show that the reflection loss values of the two kinds of coupled MEMS microwave power sensors are both smaller than -20 dB, indicating that they have good reflection performance. The insertion loss of the two kinds of coupled MEMS microwave power sensors is larger than -1. 5 dB, indicating that they have good transmission performance. The sensitivity of the system with 10% coupling degree is 1. 2 mV/ W@ 9 GHz, 1. 4 mV/ W@ 10 GHz and 0. 8 mV/ W@ 11 GHz. And the sensitivity of the system with 20% coupling degree is 2. 4 mV/ W @ 9 GHz, 2. 4 mV/ W@ 10 GHz and 1. 3 mV/ W@ 11 GHz, and they have good linearity. This article has a certain reference value for MEMS microwave power sensors.