Want to know how the manipulator with the ROV works and how it opens and closes
你指的是哪种机械臂？
单自由度机械臂
If you’re talking about the Newton Subsea Gripper the video on the page explains how it works, and the Technical Details and Learn sections at the bottom describe the extent of motion and the required PWM signal to open/close the gripper.
请问夹持器是什么驱动它张开闭合的，直流电机吗？
As it says in the Product Description section,
The jaws are driven by a linear actuator that uses a geared brushed motor and lead screw.
The same section also specifies that
The motor is controlled by a purpose-built brushed motor controller that accepts a standard servo-style PWM signal so that the gripper can be controlled just like our thrusters and lights.
So basically they use custom electronics to take in a PWM signal and actuate a brushed DC motor, which turns some gears (likely to improve the efficiency and increase the output torque), which turn a lead-screw, and the gripper jaws are pushed open/pulled closed by the linear motion of a carriage on the lead-screw.
Something like this:
非常感谢!!!
No worries, glad I could help 
As a note, not everyone is happy using google translate to read posts, so it might be worth trying to post questions and responses in English on the forum so that your posts are more accessible to the general community. Greater accessibility also means you’re more likely to get helpful responses from people, and it’s easier for them to learn from your posts
Thank you very much for your advice and thank you again for answering my question！ 
How’s it going? Any results yet?
Yes, we have the result. Thank you for your attention