An atmosphere transmittance meter is developed. With transmitting a beam light and detecting it, the atmosphere extinction coefficient is obtained and various weather condition can be forecasted. Prototype machine is developed and field test is done. Experiment results demonstrate the correction of test principle and technique approach. The actual measure error of atmosphere transmittance meter is approximate 10%, which is close to that of product of VAISALA in Finland. Therefore, this transmittance could meet the demand of practical application.