Abstract: The water needed for dryland wheat growth is provided by soil moisture and rainfall. To some extent, the wheat yield is determined by soil moisture before sowing. This study aimed to analyze the relationship between the grain filling process and water consumption in the Loess Plateau (China), and investigate the response of dryland wheat yield to soil moisture before sowing and phosphate fertilizer. A field experiment was conducted in the southern Shanxi Province of China. There were two factors in the experiment:1) soil moisture before sowing in the 0-100 cm soil layer, including three levels at W1 (248 mm), W2 (233 mm), and W3 (205 mm); and 2) phosphorus fertilizer rates at P1 (75 kg·hm^-2) and P2 (180 kg·hm^-2). We first investigated the changes in total wheat water consumption, soil water consumption, water consumption during each growth stage, yield and yield components, and grouting process under different treatments. Collected data were analyzed using multiple regression with a Logistic fit. The results showed that soil moisture before sowing had a significant effect on water consumption during the greening-jointing and jointing-anthesis stages. The total water consumption during the growth period, the soil water consumption, and the proportion of total water consumption, yield, spike, and thousand-grain weights were also influenced significantly by soil moisture before sowing. Compared with W3, yields of W1 and W2 significantly increased by 14.89% and 8.66%, respectively. Phosphate fertilizer has a significant effect on yield, spike, thousand-grain weight and water consumption in the wheat sowing-greening, greening-jointing, and jointing-anthesis stages. With the increase of phosphorus fertilizer, sowing-jointing water consumption decreased and jointing-anthesis water consumption, yield, and thousand-grain weight increased. The wheat grouting equation showed that the duration of the fast increase period increased with increasing soil moisture before sowing, and the duration of the increasing period and the fast-increasing period both increased with increasing phosphate fertilizer rate. The coefficient of variation of grain increased by 25% during the slow-increasing period; the wheat water (phosphorus) fertilizer equation showed that high yield can be obtained at the 0-100 cm soil moisture boundary before sowing at 253 mm. Additionally, with the same soil moisture before sowing, the yield increased with increasing phosphorus fertilizer rate. The results show that the water consumption of dryland wheat in the jointing-anthesis stage was sensitive to soil moisture before sowing and phosphate fertilizer application. The duration of the fast-increasing period in the filling process had a better response to soil moisture before sowing and phosphate fertilizer, and the variation of the slow-increasing period impacted on grain weight.