From performances of concrete,striping time,loading of floor, human factors and other aspects reasons caused the cracks in cast-in-place floor are analyzed;at the same time corresponding technical measures are proposed in order to ensure construction quality of floor.

Based on the investigations on the floor live load and resistance parameters of typical residential buildings,such as the material strength and dimension tolerance of structural members,the present reliability level of residential buildings is studied,and the structural reliability as the result of altering the value of floor live load and increasing load when the room is deco.

The multistorey and high-rise residential buildings in Xi an and Baotou,added up to 105 residents,465 rooms are investigated in the paper,and a great quantity of residential floor live load data are expressed in terms of uniformly distributed loads with the average load in batten area and room area.