In this paper, a system on a programmable chip (SOPC) based remote environment monitor system (REMS) is proposed. The REMS has two components to be responsible and are respectively: (1) Sensirion SHT10 sensor, and (2) DM9000C network interface card (NIC). The Sensirion SHT10 sensor is used to detect the temperature and the relative humidity. The NIC is an Ethernet component and used to transmit the sensor values to the other monitor devices via Ethernet. The SOPC technology that includes a Nios II processor and many peripheral devices is integrated into the field programmable gate array (FPGA). Moreover, a hardware and software co-design method is applied to the REMS. For catching the sensor values, a 2-wires serial interface module is implemented by the Verilog hardware description language (HDL). In the NIC hardware design, a DM9000C interface is integrated into REMS and connected to the NIC. In the software design, we integrate a uIP software package that includes a TCP/IP protocol into the REMS and control the Ethernet communication. In the experiment results, the temperature and relative humidity can be obtained via Ethernet from the REMS. An app of android mobile client is developed to receive the temperature and relative humidity data and observed the system.