Abstract: 13 of wheat cultivars were subjected to 4 artificial daylength treatments at ranging 10,12. 5,15, 24 hours and natural daylength in Guangzhou. The experiments were made in the winter of 1985 and 1987, which had 3 and 4 sowing date, respectively. The results are shown as follows: winter varieties strictly had the critical heading daylengtns (CHD), and presented a stabler heading days under the daylength longer than CHD. The CHD was not discovered in the spring and semi-winter varieties, but the heding date was found much earlier in longer daylength treatments. The heading date of spring varieties from South China or Sichang province or Ninxia Hui atonomous region and of semi-winter varieties from Shandong province had a relation with the daylength and temperature as such equation expressed, y = a-b1X1-b2X2. And the heading date of the spring varieties from South China were mor sensitive to the daylength than the temperature. In contrast the spring varieties from Sichang and Ninxia and the semi-winter varieties from Shandong were sensitive to the temperature. The relation of heading date with daylength and the temperature in the winter varieties were expressed in the equation: y=a-b1X1+b2X2. It showed that the heading date was more affected by temperature than by daylength. Some effects of the daylength to wheat growth duration and yield components were also discussed in the artical.