The invention provides a sensor arrangement optimization method for obtaining soil humidity. The sensor arrangement optimization method comprises the following steps: step S1, arranging a plurality of sensors in a soil region to be measured and obtaining measurement data of the plurality of sensors at different moments; carrying out sparse representation on the measurement data at any moment to obtain sparse coefficients; step S2, based on the sparse coefficients and a measurement matrix, carrying out reconstruction operation by adopting a reconstruction algorithm to obtain estimated value of the measurement data, wherein each row of the measurement matrix only has one element 1 and each line at least has one element 1; step S3, comparing the measurement data at the different moments with the corresponding estimated value of the measurement data to obtain errors; determining a deployment quantity and deployment positions of the sensors based on the estimated value of the measurement data, which has the smallest error. The sensor arrangement optimization method for obtaining the soil humidity, provided by the invention, has high measurement accuracy and a small utilization quantity of the sensors.