Abstract: Deformation monitoring is carried out in gob-side entry retaining of Zhongxing Mine. Floor heave laws which be in the firstly and secondary mining are studied by analyzing working resistance's changes of hydraulic supports and deformations of roadway. The results show that: Deformation of floor heave in Gob-side Entry Retaining related to multiple factors, forms and formation condition, the condition of surrounding rock and supporting water conditioning are important factor of floor heave. According to the floor heave of monitoring data, the variation of the floor heave with the mining face is divided into four periods: excavation and the stability, firstly mining front support influence period, firstly mining post influence period and secondary mining front support influence period. Among them firstly mining post influence period and secondary mining front support influence period produce more than 90% of the floor heave. The secondary mining effect of floor heave is far greater than the firstly mining period.