using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class player : MonoBehaviour
{
    public GameObject PrintPrefab;
    // Use this for initialization
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        //Debug.Log(Camera.main.ScreenToWorldPoint(Input.mousePosition)+new Vector3(0,0,10));

        Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition) + new Vector3(0, 0, 10);

        transform.position = mousePos;
        if (Input.GetMouseButton(0))
        {
            Instantiate(PrintPrefab, transform.position, transform.rotation);
        }
    }
}

代码解析：
1.屏幕坐标转化为三维坐标

Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition) + new Vector3(0, 0, 10);

2.物体跟随鼠标移动

transform.position = mousePos;

3.创建预制体

if (Input.GetMouseButton(0))
 {
                          Instantiate(PrintPrefab, transform.position, transform.rotation);
}

把脚本给一个空物体就行。空物体的坐标为(0,0,0)，旋转坐标为(0,0,0)