Basing on the dual-wavelength high altitude detecting lidar that we have developed, the daytime observation ability has been realized in its sodium fluorescence channel by employing Na (sodium) atomic optical filter and other relevant technologies. Because of very narrow passband and very high out-of-band suppression of the Na atomic optical filter, the lidar echo at 80～110 km altitude can be obtained even in the noon-time when the background light from the sun is very strong. The ability of 24 hours continuous observation of the lidar system has been demonstrated by the preliminary observation result. This development makes the all time detection and investigation of high altitude atmosphere over our country becoming possible.