The differences among these sentences:"i miss you" "i have missed you" "i missed you". Thank you!
Im not quite sure about how to use them...

Question

Answer

I think actual usage examples will better help you understand the differences.
In these examples, "said" means written or spoken.

~"I miss you."
...Said (by phone) to someone who is not there.
...You miss them right now, as you speak.
...Or, said with a qualifier, to someone who has returned:
...~"When you are not here, I miss you."

~"I have missed you."
...Said to a person who has now returned.
...Said to a person who is still away.
...You are stating your feeling up to that point in time.

~"I missed you."
...Said to a person who is now back.
...Your feeling is in the past.
...Or, said with a qualifier to someone who is still away:
...~"I missed you for a long time, but not anymore."

Ah, the beautiful simplicity of a single " 我想你。"

Answer

I miss you - present tense- u miss now!
i have missed you -present perfect- from few days till now, he/she is still absent! 
i missed you -past simple- u missed him before when he/she wasn't here!!

Đừng bỏ lỡ cơ hội học ngoại ngữ ngay tại nhà. Hãy xem danh sách các gia sư ngôn ngữ giàu kinh nghiệm của chúng tôi và đăng ký buổi học đầu tiên ngay hôm nay!