In order to explore the feasibility of different data assimilation algorithms in monitoring soil salinity on the spatio-temporal scale, the Shahaoqu Canal Irrigation Area in Hetao Irrigation District of Inner Mongolia was taken as the research area, and the Gaofen-1 satellite remote sensing image was used as the data source. The assimilation observation operator and model operator of EnKF algorithm and PF algorithm were used to obtain the changes of soil salinity in the spatio-temporal range. The observation operator was divided into two steps, firstly, the PLS-VIP criterion was used to filter the spectral index as the independent variable, and then the ELM model was used to establish the remote sensing monitoring soil salinity model based on different depths at different times; the model operator was a mathematical simulation monitoring soil salinity model based on the Hydrus-1D model. The results showed that in the ELM-based soil salinity model, the average IOA at the depths of 0~20cm, 20~40cm and 40~60cm were above 0.74, and the average ME was below 0.14%, indicating that the inversion model had good accuracy; in the Hydrus-1D based mathematical simulation monitoring soil salinity model, the average IOA at the three depths was between 0.79 and 0.89 and the average ME was between 0.128% and 0.137%, which could better reflect the transport of soil salts in the time series; the EnKF algorithm had IOA above 0.820 for three depths, ME between 0.141% and 0.157% and NMB between 0.141 and 0.252, and the PF algorithm had IOA above 0.89 for three depths and ME ranged from 0.090% to 0.142% and NMB ranged from 0.075 to 0.097, with better accuracy than the EnKF algorithm, which can well reflect the distribution of soil salinity in time and space. The assimilation scheme of Hydrus-1D model and ELM model based on EnKF and PF algorithms improved the accuracy of monitoring soil salinity, which can provide a basis for subsequent monitoring of soil salinity on a long time and large spatial and temporal scale, and can also provide a reference for the research of precision agriculture to control soil salinity.