In this paper, design and development solar energy watering cassava crop systems with systems control by smartphone is presented. The objective is study the performance of the watering system by smartphones. The hardware component was Arduino Uno, Wi-Fi module, water pump, relay, solar panels, battery, smart phone and blynk applications, respectively. The design and development of the prototype watering cassava crop system with controlled by smartphones and write program command code for systems control by using blynk applications. This research was studied working distance in case with or without obstruction and studied working of water pump and solenoid valve, respectively. From the experiment results of the solar energy watering cassava crop systems that smartphone can ON-OFF solenoid valve to open or close water flow of 0-50 meters (diameter =100 m) in case without obstruction, 0-30 meters (diameter = 60 m) in case with obstruction, working distance of moisture sensor of 0-90 meters, water pump and solenoid valve can work precisely, respectively. Moreover, the experimental results of monitoring of watering cassava crop system by smartphone as follows: the average temperature of 36C°, average ambient humidity of 50%, and average soil moisture of 60%, respectively. Therefore, the watering cassava crop systems with systems control using smartphone can use for the communities to reduce time, increase efficiency and increase the productivity of the community sustainably.