The influence of diurnal temperature variation on land-sea breeze in peninsula region on the coast south of the Bohai bay was approached by using data collected at several observatories. The reversal of breeze direction between day and night exists throughout the year in regular pattern, a consequence of the effect of unevenly heated land and sea. The reversal time and duration vary with the four seasons. Although land-sea breeze makes no obvious harm,it has much to do with the advection and abation of sea fog and growth of southwest wind at night in the region.