To design a wireless transmission system for water temperature data detection .This system uses FM as modulation scheme. The launching part adopts MC12017 and MC145152 as PLL, enabling to decrease the carrier frequency error to 1.8×10-4. The carrier frequency modulation is achieved by transfiguration diode HS113 and integrated VCO MC1648. The final stage amplifier adopts triode 2SC2053 with transmission power amounting to 0.245 mw. The receiving part adopts FM receiver chip MC3362 with low consumption and narrowband as main body, analog signals being amplified by LM386. C8051F410 is used as the control chip in the whole system to decode, frequency measure, and display. Experimental tests show that this system consumes lower power, reliable and steady, and is able to correctly transmit and receive data.