This paper proposes an intruder detection method using Multiple Input Multiple Output channel. We call this method as MIMO Sensor. Although the channel capacity on the MIMO transmission is severely degraded in time variant channels, we use this feature as an underhanded way in the MIMO Sensor. The time correlation function for channel matrix of MIMO channel is used as the cost function. Moreover, we clarify the antenna arrangement (antenna height and element spacing) which is suitable for MIMO sensor by using the measured propagation channels in an indoor environment. From the measured results, we clarify that the antenna hight with 1 m and the element spacing over 22 λ are suitable for MIMO sensor, when considering the small room (53 m2) when considering 2×2MIMO sensor.